Sierra AI vs PolyAI Comparison (2025)
Sierra AI
Starting at $2 per successful outcome
Sierra AI delivers a comprehensive conversational platform with multi-channel voice and chat, real-time analytics, and enterprise-grade security out of the box. But you won’t find a price list anywhere—expect to negotiate usage-based fees that climb steeply as you add advanced features or extra channels. Its “build once, run everywhere” Agent OS sounds neat, but customizing flows and integrating with legacy systems often requires dedicated engineering time. The command center offers deep controls, yet teams frequently find it overengineered for routine tasks and in need of training to manage. And despite claims of empathetic, human-like responses, at scale the agents can still stumble over accents or complex queries, leaving gaps that demand human intervention.
Key Metrics
Latency
800 ms
Automation
60%
Integrations
30
Onboarding
7 days
Sierra AI
Score
79
Latency
800 ms
Automation
60%
Integrations
30
Onboarding
7 days
Cost
Low
HIPAA Compliant
Yes
PolyAI
Score
67
Latency
1700 ms
Automation
72%
Integrations
25
Onboarding
60 days
Cost
Medium
HIPAA Compliant
Yes
Sierra AI
Sierra AI delivers a comprehensive conversational platform with multi-channel voice and chat, real-time analytics, and enterprise-grade security out of the box. But you won’t find a price list anywhere—expect to negotiate usage-based fees that climb steeply as you add advanced features or extra channels. Its “build once, run everywhere” Agent OS sounds neat, but customizing flows and integrating with legacy systems often requires dedicated engineering time. The command center offers deep controls, yet teams frequently find it overengineered for routine tasks and in need of training to manage. And despite claims of empathetic, human-like responses, at scale the agents can still stumble over accents or complex queries, leaving gaps that demand human intervention.
PolyAI
Poly AI positions itself as a multilingual powerhouse with natural-sounding agents and enterprise use cases. But without public pricing, you’ll need to talk to sales before understanding costs—and anything outside standard English can trigger custom pricing. Integrations work fine if you’re on Salesforce or a mainstream stack, but anything else means custom development. In real use, the assistant occasionally forgets context or asks you to repeat yourself, which breaks the illusion fast. For all the polish, it often feels like a heavy lift to get consistent, high-quality performance.
Full Comparison
| Vendor | Score | Latency | Automation | Integrations | Cost | Action |
|---|---|---|---|---|---|---|
 OpenCall.ai $0.10/ minute | 93 | 700 ms | 76% | 2000 | Low | |
 Retell.ai $0.07 – 0.08 /min | 82 | 950 ms | 55% | 25 | Low | |
Sierra AI $2 per successful outcome | 79 | 800 ms | 60% | 30 | Low | |
PolyAI $0.25 /min (example case study) | 67 | 1700 ms | 72% | 25 | Medium | |
 Bland AI $0.09/min | 66 | 1100 ms | 50% | 15 | Low | |
 Phonely $396 (yearly) | 61 | 1200 ms | 52% | 17 | Medium | |
 Hey Rosie $49/mo (250 min) + $0.25/min | 57 | 950 ms | 60% | 1 | Low | |
 Smith.ai $3.25 /call (Starter 30 calls @ $97.50/mo) | 55 | 2300 ms | 40% | 30 | Medium | |
 8x8 XCaaS $60 per seat per month | 49 | 250 ms | 50% | 15 | Medium | |
 CloudTalk $25 – $50 /user/mo | 47 | 23 ms | 40% | 500 | Low | |
 Synthflow AI $0.08 /min (Growth) | 20 | 2300 ms | 45% | 20 | Low | |
 Balto.ai $100 / seat /mo | 12 | 100 ms | 0% | 40 | High |