We used Oden to analyze public websites, pricing pages, G2 reviews, and real Reddit discussions comparing Responsive.io, Klaviyo, Attentive, and Postscript. If you’re trying to pick an SMS marketing platform, you’ve probably noticed that these tools look similar on the surface but behave very differently once you’re inside them. One important caveat up front: Responsive.io is an AI-powered RFP/Strategic Response Management platform, not an SMS marketing platform, so we’ll call out where the comparison isn’t apples to apples. Source: Responsive website(responsive.io) Instead of generic pros and cons, this guide focuses on ratings, pricing structures, feature depth, and where each tool realistically fits.

Which SMS marketing platform has the best rating?

To keep things comparable, we’ll use overall G2 product ratings and review counts as of December 14, 2025. These reflect broad product satisfaction (not just SMS), but they’re still useful directional signals.

Takeaways

• Postscript has the highest average rating (4.9) but on a much smaller review base (159), so individual experiences may weigh more heavily than with the larger tools. Source: G2 – Postscript()
• Klaviyo and Attentive both sit at 4.6 with ~1,100 reviews each, suggesting consistently strong satisfaction across a wide user base for marketing automation and SMS. Source: G2 – Klaviyo, G2 – Attentive(g2.com)
• Responsive.io’s 4.5 rating and >1,200 reviews show it’s a mature, trusted platform—just for a different problem (complex RFPs and questionnaires), not outbound SMS marketing. Source: G2 – Responsive()
• For SMS-specific work, user sentiment clusters around Attentive as a premium “white glove” option, Klaviyo as an integrated email+SMS workhorse, and Postscript as a specialized Shopify SMS engine. Source: Attentive marketing site, Klaviyo SMS page, Postscript homepage(attentive.com)
• None of these ratings are “statistically perfect”; they’re self-reported and can change frequently, so treat them as directional rather than absolute benchmarks.

How much do SMS Marketing platforms really cost?

Pricing is where the tools diverge sharply. Below is a simplified snapshot; discounts, add-ons, and enterprise deals can change the math significantly.

What this means in practice

• If you want SMS tightly bundled with email and a CRM-like profile model, Klaviyo’s Email + SMS pricing can be cost-effective versus running separate platforms, especially under ~50k profiles. Source: Klaviyo pricing()
• If SMS is a major revenue driver and you want aggressive optimization plus direct control over per-message rates, Postscript’s transparent per-SMS pricing and $0 base plan make it easy to model ROI, though there is a practical minimum spend. Source: Postscript pricing(postscript.io)
• Attentive tends to fit brands that are comfortable with custom, usage-based quotes in exchange for an AI-heavy, white-glove SMS/email program and deep strategic support. Source: Attentive pricing, Attentive “Why choose us”()
• Responsive.io is essentially “orthogonal” to SMS pricing; for marketing teams it’s an additional spend on top of whatever SMS platform you choose, justified only if you manage a heavy volume of RFPs and questionnaires. Source: Responsive website(responsive.io)

Pricing varies by region, message type, carrier fees, list size, and contract terms. Always double-check current prices with each vendor's calculator or sales team.

What are the key features of each platform?

Responsive.io

Core positioning: AI-powered Strategic Response Management platform for RFPs, questionnaires, and complex information requests—not an SMS campaign tool. Source: Responsive website(responsive.io)

Key Features:

• AI “agents” trained on millions of Q&A pairs to draft answers to RFPs, RFIs, security questionnaires, and other forms, aiming to cut response time dramatically. Source: Responsive homepage(responsive.io)
• Centralized content library with unlimited storage and review workflows, so teams can maintain vetted answer banks and reuse approved language. Source: Responsive pricing page()
• Collaboration tools that let sales, proposal managers, and SMEs co-author responses with role-based permissions and integrated notifications. Source: G2 – Responsive()
• Analytics on response activity, win rates, and content performance to understand which answers and teams drive revenue. Source: Responsive press release()
• Integrations with CRM and collaboration tools like Salesforce, Slack, and Microsoft Teams to embed RFP workflows in existing stacks. Source: Responsive overview(responsive.io)

Best For:

• B2B companies responding to frequent RFPs, security questionnaires, and complex due diligence requests.
• Revenue, proposal, or InfoSec teams that need AI-accelerated content reuse and compliance, separate from marketing channels.
• Organizations that already have an SMS/email platform but struggle with manual proposal work.

Klaviyo

Core positioning: Unified customer platform where email, SMS, and other channels run from one data-rich CRM-style hub. Source: Klaviyo product overview(klaviyo.com)

Key Features:

• SMS marketing built on a shared data platform, enabling granular segments, behavioral triggers, and coordinated email + SMS flows. Source: Klaviyo SMS page(klaviyo.com)
• Built-in AI (K:AI) for content generation, send-time optimization, and automated SMS conversations answering FAQs and recommending products. Source: Klaviyo SMS page(klaviyo.com)
• 350+ integrations (Shopify, BigCommerce, Salesforce, etc.) that pump ecommerce and behavioral data into unified customer profiles. Source: Klaviyo pricing page()
• Visual flow builder supporting multi-channel automations (welcome, abandoned cart, post-purchase, winback) that mix email, SMS, and push. Source: Klaviyo SMS documentation
• Multi-channel attribution and reporting to avoid double-counting revenue across email and SMS. Source: Klaviyo SMS page(klaviyo.com)

Best For:

• Ecommerce and DTC brands that want email + SMS + data platform under one roof.
• Teams with moderate technical sophistication that value deep segmentation and automation over extreme simplicity.
• Agencies or in-house teams managing many flows and needing robust integrations and reporting.

Attentive

Core positioning: AI-powered SMS and email marketing platform focused on mobile-first personalization and enterprise-grade compliance. Source: Attentive homepage(attentive.com)

Key Features:

• SMS, MMS, email, and RCS messaging in one platform, with mobile-first identity to coordinate campaigns across channels. Source: Attentive homepage(attentive.com)
• Patented two-tap signup and advanced list-growth tools to convert mobile visitors into SMS/email subscribers quickly. Source: Why Choose Attentive(attentive.com)
• Attentive AI for copywriting, send-time optimization, segmentation, and conversational assistants trained on trillions of interactions. Source: Why Choose Attentive(attentive.com)
• Built-in compliance guardrails and legal tooling designed to reduce TCPA and carrier-related risk. Source: Why Choose Attentive(attentive.com)
• 100+ integrations with ecommerce, CRM, and advertising tools, plus detailed analytics and audience management. Source: Why Choose Attentive(attentive.com)

Best For:

• Mid-market and enterprise ecommerce brands that want a high-touch, mobile-first program with strong strategic guidance.
• Teams that need sophisticated list growth and compliance and are willing to pay for a premium solution.
• Brands prioritizing AI-driven optimization across both SMS and email.

Postscript

Core positioning: SMS-first marketing and sales platform built primarily for Shopify brands that want SMS to be a top revenue channel. Source: Postscript homepage(postscript.io)

Key Features:

• Deep Shopify integration and SMS-specific automation triggers (cart, browse, shipping, subscription events, etc.) tailored to ecommerce flows. Source: Postscript features(postscript.io)
• Visual Flow Builder for two-way SMS conversations, campaigns, and automations, with in-flow analytics. Source: Postscript features(postscript.io)
• AI “Infinity Testing” to explore many copy variants and optimize for revenue lift, plus AI brand voice training and conversational assistants. Source: Postscript features(postscript.io)
• Strong compliance tooling and in-house legal focus to hard-wire TCPA and carrier rules into list-growth and messaging flows. Source: Postscript pricing/compliance section(postscript.io)
• Flexible pricing with per-message rates, dedicated toll-free numbers, and optional SMS “Sales” services and AI add-ons. Source: Postscript pricing(postscript.io)

Best For:

• Shopify and Shopify Plus stores that want an SMS-first strategy with specialized tooling and support.
• Brands ready to scale SMS revenue and comfortable paying per-message plus a plan fee.
• Teams that want heavy experimentation, two-way SMS commerce, and hands-on guidance from SMS specialists.

What are the strengths and weaknesses of each platform?

Responsive.io

Strengths:

• Users consistently report major time savings on RFPs and questionnaires, often cutting efforts from days to hours thanks to AI-assisted answer suggestions and content reuse. Source: G2 – Responsive()
• Robust, centralized content library with export tools and review workflows is praised for keeping complex knowledge bases organized and searchable. Source: G2 – Responsive()
• Strong collaboration features across sales and SMEs, with many reviews noting easier coordination and higher win rates. Source: Responsive press releases()
• Frequently recognized by G2 as a category leader in RFP and proposal software for many consecutive quarters, which indicates consistent customer satisfaction. Source: Businesswire – G2 leader announcements()

Weaknesses:

• Many reviewers mention a steep learning curve and “busy” UI with too many views and buttons, making onboarding harder for casual users. Source: G2 – Responsive()
• Search and AI responses can be imperfect, sometimes requiring manual refinement or additional filtering to find the right answers. Source: G2 – Responsive()
• Basic text-editing and table formatting inside the tool are described as limited, pushing teams back into Word for complex layouts. Source: G2 – Responsive()
• For SMS marketing use cases, Responsive simply doesn’t compete—it’s not designed for list growth, campaign management, or compliance in SMS. Source: Responsive website(responsive.io)

Klaviyo

Strengths:

• Users praise Klaviyo’s balance of power and usability for email and SMS, citing an intuitive template builder and relatively fast time to initial campaigns. Source: G2 – Klaviyo(g2.com)
• Deep integrations (350+ apps) and a strong data platform make it easy to build granular segments and behavior-based flows that span email and SMS. Source: Klaviyo pricing, Klaviyo SMS page()
• Multi-channel attribution and reporting help avoid double-counting revenue between SMS and email, useful for channel budget decisions. Source: Klaviyo SMS page(klaviyo.com)
• Free plan lets small brands test email + limited SMS before upgrading, lowering adoption friction. Source: Klaviyo pricing()

Weaknesses:

• Some G2 reviewers note cluttered UI areas (like segment management) and manual cleanup steps that can slow down heavy users. Source: G2 – Klaviyo(g2.com)
• Support is often described as primarily email- or ticket-based with limited live chat, which can feel slow under time pressure. Source: G2 – Klaviyo(g2.com)
• SMS compliance guidance is seen by some practitioners as relatively “hands-off”; one Reddit discussion calls Klaviyo the “most relaxed” platform on compliance compared with Attentive and Postscript, placing more responsibility on brands to implement best practices. Source: Reddit – Klaviyo SMS compliance
• As list sizes and send volumes grow, users frequently describe Klaviyo as expensive relative to more narrowly focused tools. Source: G2 – Klaviyo(g2.com)

Attentive

Strengths:

• G2 reviewers consistently highlight Attentive’s ease of use and intuitive UI for setting up campaigns, automations, and list-growth units. Source: G2 – Attentive()
• Customer support and onboarding are repeatedly described as “white glove,” with dedicated CSMs and integration assistance that go beyond basic support. Source: G2 – Attentive()
• Official positioning as a G2 SMS Marketing leader and results like 181% ROI in commissioned Forrester studies reinforce its premium, performance-focused brand. Source: Attentive G2 landing
• Strong AI tooling and multi-channel coordination (SMS, email, RCS) make it appealing for brands wanting enterprise-scale personalization. Source: Why Choose Attentive(attentive.com)

Weaknesses:

• Many users describe Attentive as more expensive than other SMS providers; several G2 reviews explicitly mention steep pricing as lists grow. Source: G2 – Attentive()
• Some marketers find advanced segmentation and reporting less flexible or intuitive, requiring more effort to build nuanced journeys. Source: G2 – Attentive()
• Session timeouts and frequent re-authentication steps are a recurring annoyance in user feedback. Source: G2 – Attentive()
• A Reddit thread comparing signup forms notes some limitations in Attentive’s form features when trying to pass complex survey-style properties into Klaviyo, indicating extra configuration for advanced data capture. Source: Reddit – Attentive + Klaviyo forms

Postscript

Strengths:

• Very high G2 rating (4.9) with reviews emphasizing Shopify-native workflows, ease of use, and responsive support. Source: G2 – Postscript()
• SMS-first product design with many ecommerce-specific triggers (inventory, price drops, shipping, subscriptions) and conversational flows. Source: Postscript features(postscript.io)
• Transparent per-SMS pricing and strong emphasis on compliance, including an in-house legal team and product-led guardrails. Source: Postscript pricing(postscript.io)
• Very tight alignment with Shopify merchants, reinforced by case studies and external coverage describing it as a core SMS provider for Shopify ecosystems. Source: Postscript homepage, TechCrunch profile(postscript.io)

Weaknesses:

• Historically focused on Shopify; while an SDK exists for non-Shopify stores, several reviews and docs make clear that the best experience is on Shopify, which limits flexibility for multi-platform retailers. Source: G2 – Postscript, Postscript FAQ()
• Shopify App Store reviews and Reddit posts mention confusion over a “$0” plan that still carries a minimum monthly charge (e.g., $25–$30) even with no sends, plus frustration over refunds. Source: Shopify App Store – Postscript reviews
• Some technical threads report occasional integration or verification issues (e.g., verification codes not arriving on password pages), requiring support or custom workarounds. Source: Reddit – Postscript verification issue
• A fresh Reddit discussion points out that Postscript doesn’t support a single unified email+SMS popup natively, leading some brands to consider switching to Klaviyo or other tools for forms. Source: Reddit – Postscript popup limitations

How do these platforms position themselves?

Responsive.io frames itself as “the leader in Strategic Response Management & RFP software,” emphasizing AI agents that draw from large Q&A libraries to help teams respond to RFPs, RFIs, security questionnaires, and similar information requests faster and more accurately, with claims of billions of dollars in opportunities managed. Source: Responsive website, Responsive press releases(responsive.io)

Klaviyo markets itself as a unified customer platform and B2C CRM that orchestrates email, SMS, and other channels from a single data platform, with messaging like “SMS marketing built for smarter sends” and strong emphasis on AI and integrated data for personalization. Source: Klaviyo SMS page, G2 – Klaviyo product description(klaviyo.com)

Attentive leans heavily into being “the leader in mobile” and an “AI-powered SMS and email marketing platform,” highlighting two-tap mobile signups, AI personalization, and 8,000+ brand customers as proof of performance and scale. Source: Attentive homepage, Why Choose Attentive, Attentive G2 landing(attentive.com)

Postscript positions itself directly as “SMS Marketing and Sales for Shopify Brands” and explicitly states its mission to make SMS the #1 revenue channel for ecommerce merchants, emphasizing list growth, conversational commerce, and compliance as core differentiators. Source: Postscript homepage, Postscript careers/job ad(postscript.io)

Which platform should you choose?

Below are practical guidelines based on your use case, tech stack, and tolerance for complexity and cost.

Choose Responsive.io If:

1. You need to dramatically speed up RFPs, security questionnaires, and due diligence responses and are willing to use a separate tool for SMS marketing. Source: Responsive website(responsive.io)
2. Your sales, proposal, and InfoSec teams spend dozens of hours per month answering repetitive questionnaires and want AI-assisted drafting plus a shared content library. Source: G2 – Responsive()
3. You’re a mid-market or enterprise B2B company dealing with large, complex deals where higher win rates and faster responses justify a specialized SRM budget. Source: Responsive press releases()
4. You want centralized governance and analytics around proposal content, including who’s using which answers and how they affect wins. Source: Responsive overview(responsive.io)
5. You already have or plan to adopt a dedicated SMS platform (Klaviyo, Attentive, Postscript, or others) and are evaluating Responsive as a complementary system, not a replacement.

Choose Klaviyo If:

1. You want email and SMS in the same platform and care about unified profiles, cross-channel flows, and consolidated reporting more than having the absolute deepest SMS-only feature set. Source: Klaviyo SMS page(klaviyo.com)
2. You’re on Shopify, BigCommerce, or another mainstream ecommerce platform and want robust integrations for behavioral triggers (browse, cart, purchases) across channels. Source: Klaviyo pricing/integrations()
3. You value having a free tier to test SMS alongside email before committing to higher send volumes or large lists. Source: Klaviyo pricing()
4. You have (or can access) solid SMS compliance expertise—internally or via an agency—since Klaviyo gives flexibility but expects you to implement best practices. Source: Reddit – Klaviyo SMS compliance
5. You want to layer AI-powered testing, segmentation, and conversational agents on top of both email and SMS without buying separate point solutions. Source: Klaviyo SMS page(klaviyo.com)

Choose Attentive If:

1. SMS and email are already significant revenue channels and you’re comfortable with a premium, usage-based platform that emphasizes AI and white-glove support. Source: Attentive pricing, Why Choose Attentive()
2. You want aggressive list growth via mobile-first signup experiences (two-tap popups, onsite mechanisms) and are optimizing heavily for mobile conversion. Source: Why Choose Attentive(attentive.com)
3. You prioritize compliance and deliverability, especially if you’ve had prior issues or legal exposure around SMS. Source: Why Choose Attentive, Attentive G2 landing(attentive.com)
4. You want a partner-style relationship where a CSM and strategy team help design and iterate campaigns, not just provide software. G2 reviews repeatedly highlight this as a differentiator. Source: G2 – Attentive()
5. Your team prefers a tool purpose-built for mobile engagement rather than a broader marketing automation platform where SMS is one of many channels.

Choose Postscript If:

1. You’re on Shopify (or Shopify Plus) and want SMS to be a primary, high-ROI revenue channel with deep ecommerce-specific triggers and flows. Source: Postscript homepage, Postscript features(postscript.io)
2. You care about clear per-SMS pricing and want fine-grained control over spend, including the ability to start small with a $30 minimum and scale up as ROI becomes clear. Source: Postscript pricing(postscript.io)
3. Compliance risk keeps you up at night and you’d rather have a product that enforces strict rules by design than rely on internal checklists. Source: Postscript pricing/compliance section(postscript.io)
4. You want advanced SMS experimentation (AI Infinity Testing, conversational flows, SMS Sales services) and are ready to invest in testing and optimization to make SMS your #1 revenue channel. Source: Postscript features(postscript.io)
5. You’re okay with relying on Shopify-native or custom solutions for forms and popups, or you’re willing to supplement Postscript with other form tools when you need combined email+SMS capture. Source: Reddit – Postscript popup limitations

Sources & links

Company Websites

• Responsive.io website
• Klaviyo website
• Attentive website
• Postscript website

Pricing Pages

• Responsive – Pricing
• Klaviyo – Pricing
• Attentive – Pricing
• Postscript – Pricing

Documentation

• Klaviyo – How to create and send an SMS campaign
• Klaviyo – SMS marketing overview
• Attentive – Why Choose Attentive
• Postscript – Features
• Postscript – Help Center

G2 Review Pages

• G2 – Responsive (formerly RFPIO)
• G2 – Klaviyo
• G2 – Attentive
• G2 – Postscript

Reddit Discussions

• Klaviyo SMS compliance (lack thereof)
• Switching signup forms between Postscript, Attentive, and Klaviyo
• Postscript – Single popup for email/SMS?
• Postscript verification code not working
• Postscript hiring post describing mission and focus

Additional Resources

• Responsive rebrand to Strategic Response Management
• Responsive G2 leadership press release – Winter 2025
• Attentive – G2 SMS Marketing leader landing
• Postscript – TechCrunch funding/profile