For SMS specifically, the public data leans Postscript. On G2, Postscript holds a 4.8-star average across 161 reviews, against Klaviyo's 4.6 across 1,360 reviews, and Postscript's reviews repeatedly single out its support team by name as a reason for the score. Klaviyo is still the better pick if you want one platform running email and SMS together off a single customer profile. But if the actual question is "which tool is built to do SMS well, and to actually answer when something breaks," the evidence points at Postscript.
The Real Difference: SMS-Native vs. SMS-Added-On
Klaviyo started as an email platform and added SMS in 2019, then kept expanding into forms, reviews, CDP features, and more, on the same core product. Postscript launched in 2018 as an SMS-only platform, built specifically for Shopify stores, and it has stayed narrowly focused on that one channel ever since.
That focus shows up in the product, not just the marketing. Postscript's two-way conversation tools include a keyword response system and message sentiment handling built specifically for how people actually text a brand back. Its compliance tooling, mandatory double opt-in, an in-house team that tracks carrier and TCPA rule changes, is purpose-built for SMS rather than adapted from an email compliance model.
What the Reviews Actually Say
| G2 Rating | Reviews | |
|---|---|---|
| Postscript | 4.8 / 5 | 161 |
| Klaviyo | 4.6 / 5 | 1,360 |
Klaviyo's much larger review count reflects its much larger install base, it's simply used by more stores overall, mostly for email. But on the specific question of support quality, the pattern in the reviews is consistent: Postscript reviewers volunteer comments like "their customer service is the best" and "some of the best customer service I've ever had" without being prompted for it. Klaviyo's reviews are more mixed on support, several call it "quick" and "thorough," but a recurring complaint is slower response times, especially for stores on lower-tier or free plans, where support has to cover email, SMS, forms, and everything else in one queue.
Klaviyo's support team covers the entire platform. Postscript's support team only has to know one channel. That's a structural reason to expect a difference, and the reviews back it up.
Where Postscript Pulls Ahead for SMS Specifically
- Support that scales with you. Live chat and email on every plan, priority live chat and email plus API access on the Professional tier, and dedicated onboarding with a personalized setup on Enterprise.
- Deliverability focus. Postscript emphasizes direct carrier relationships to protect send reliability, an area where generalist platforms using shared or unverified toll-free numbers can run into more friction.
- Built for Shopify, not adapted to it. The integration is native, not bolted on, which matters for things like real-time inventory-aware messaging and checkout-linked automations.
Where Klaviyo Still Wins
If you can only run one platform, Klaviyo is still usually the right call for most stores, because email remains the bigger revenue channel for most ecommerce brands, and having email and SMS segmentation built from the same customer profile is genuinely valuable. You're not stitching two data sources together to figure out who already got an email about the sale before you text them about it.
Not sure if the problem is the platform or the setup
Most "our SMS doesn't convert" problems aren't a platform problem. I'll look at what you're actually running before you switch anything.
The Pricing Comparison
Postscript runs on a tiered subscription plus per-message usage model. Klaviyo's SMS pricing is bundled into its Email + SMS plan, priced by active profile count.
| Postscript | Monthly | SMS Rate |
|---|---|---|
| Starter | $0 ($49 min spend) | $0.015-$0.009/msg |
| Growth | $100 | $0.01-$0.008/msg |
| Professional | $500 | $0.007/msg |
| Enterprise | Custom | Custom |
| Klaviyo Email + SMS | Active Profiles | Monthly |
|---|---|---|
| 500 | $35 | |
| 5,000 | $115 | |
| 10,000 | $165 | |
| 25,000 | $415 |
At low send volume, Postscript's usage-based model can come out cheaper. At high, consistent send volume, it depends heavily on your actual message count per profile, so run your own numbers before assuming either direction.
The Practical Answer
Most stores that actually make this decision well don't treat it as an either-or. A common, and reasonable, setup is Klaviyo for email and Postscript for SMS, run as two best-of-breed tools instead of one vendor doing both adequately. If SMS specifically is the channel that isn't performing, the public data, ratings, review sentiment, and Postscript's own tiered support structure, gives you a real reason to evaluate it seriously rather than assuming your existing platform's SMS module is as good as a dedicated one.