PolyAI vs Sierra Comparison
Compare PolyAI vs Sierra features, pricing, and more.
Last updated: November 2026
PolyAI
7.1/10
PolyAI builds enterprise voice AI agents that answer and resolve customer service calls, with chat and messaging channels, for large contact centers.
Sierra
7.4/10
Sierra is an enterprise conversational AI platform that builds and runs customer service agents across chat, voice, SMS, WhatsApp and email.
Feature-by-Feature Comparison
| Feature | | |
|---|---|---|
| Scores | ||
| Overall Rating | 7.1/10 | 7.4/10 |
| Analytics | 6/10 | 8/10 |
| Cost | 3/10 | 2/10 |
| Customization | 8/10 | 9/10 |
| Ease of Use | 6/10 | 7/10 |
| Integration | 8/10 | 8/10 |
| Output Quality | 9/10 | 9/10 |
| Scalability | 9/10 | 9/10 |
| Security | 9/10 | 9/10 |
| Support | 8/10 | 8/10 |
| Pricing | ||
| Free plan | No | No |
| Cheapest paid plan | Contact for pricing | Contact for pricing |
| Estimated cost for 10 users | Contact for pricing | Contact for pricing |
| Features | ||
| AI Agents | ||
| Chatbots | ||
| Voice and Audio | ||
| Workflow Automation | ||
| Transcription | Not listed | |
| Knowledge Base Search | ||
| API Access | Not listed | |
| Enterprise Controls | ||
| Text Generation | Not listed | |
Which One Should You Choose?
Why choose PolyAI
- Higher Cost score (3/10 vs 2/10)
Why choose Sierra
- Higher Analytics score (8/10 vs 6/10)
- Higher Customization score (9/10 vs 8/10)
Pros & Cons
PolyAI
Pros
- Reviewers repeatedly praise its natural-sounding voices and its handling of interruptions and topic changes in multi-turn calls.
- PolyAI claims around 90% end-to-end call resolution on its largest deployments and 99.994% trailing uptime.
- Compliance is strong for regulated industries: SOC 2 Type 2, ISO 27001, PCI DSS, GDPR, and US, UK, EU and APAC data residency.
- Managed pricing bundles maintenance, model upgrades, integrations and 24/7 support.
- One agent can serve voice, SMS, WhatsApp, web chat and email.
- G2 reviewers describe support as responsive during implementation.
Cons
- The platform has no public price, so buyers must go through a sales-led quote.
- Some users report occasional lag or slow responses.
- Reviewers want deeper voice analytics and reporting.
- It can struggle with complex or unusual interactions.
- It relies on underlying telephony providers rather than bundling a full phone system.
- It is oriented toward large enterprises, which makes it a poor fit for small teams.
Sierra
Pros
- Outcome-based billing means customers usually pay only for resolved conversations or other agreed results, not for each seat.
- Three build options cover both CX teams and engineers: the no-code Agent Studio, the code-first Agent SDK, and Ghostwriter for building agents from SOPs.
- One agent runs across chat, voice, SMS, WhatsApp, email and ChatGPT, keeping context between channels.
- Its list of compliance attestations is broad, covering SOC 2, ISO 27001, ISO 42001, HIPAA, PCI DSS and FedRAMP.
- It has a strong roster of enterprise customers, including SiriusXM, ADT, Rocket Mortgage and SoFi.
Cons
- There is no public pricing, and competitor estimates put annual contracts at about $150,000 or more.
- There is no self-serve or trial tier, so small teams cannot try it on their own.
- Implementation is largely vendor-led, which can make customers depend on Sierra's team for changes.
- There are few public reviews (7 on Gartner Peer Insights) to verify claims against.
- Some reviewers say voice quality still falls short of human level, and that complex telephony setups depend on how far the integration goes.
