Sierra AI vs Phonely Comparison (2025)

Sierra AI

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
Sierra AI
Score
79
Latency
800 ms
Automation
60%
Integrations
30
Onboarding
7 days
Cost
Low
HIPAA Compliant
Yes
Phonely
Phonely
Score
61
Latency
1200 ms
Automation
52%
Integrations
17
Onboarding
1 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.

Phonely

Phonely AI bills itself as a half-price, real-time, human-sounding receptionist, but in practice its $45–$900/month tiers hide gates around voice cloning, advanced analytics, and telemarketing workflows, forcing you into Growth or Agency plans just to unlock basic follow-up features. The voice quality can still wobble into robotic stress when handles complex queries, and “0s time to lead” claims evaporate once you factor in the manual routing tweaks and context-handoff hiccups that surface in real deployments. Integrations are limited to Google Calendar, Zapier, and a handful of CRM connectors—anything custom means wrestling with their sparse API docs—while the dashboard feels cluttered and the documentation skimpy. For companies seeking a truly plug-and-play AI receptionist, Phonely delivers half the promise but twice the maintenance.

Full Comparison

Vendor
Score
Latency
Automation
Integrations
Cost
Action
OpenCall.ai
OpenCall.ai
$0.10/ minute
93
700 ms76%2000
Low
Retell.ai
Retell.ai
$0.07 – 0.08 /min
82
950 ms55%25
Low
Sierra AI
Sierra AI
$2 per successful outcome
79
800 ms60%30
Low
PolyAI
PolyAI
$0.25 /min (example case study)
67
1700 ms72%25
Medium
Bland AI
Bland AI
$0.09/min
66
1100 ms50%15
Low
Phonely
Phonely
$396 (yearly)
61
1200 ms52%17
Medium
Hey Rosie
Hey Rosie
$49/mo (250 min) + $0.25/min
57
950 ms60%1
Low
Smith.ai
Smith.ai
$3.25 /call (Starter 30 calls @ $97.50/mo)
55
2300 ms40%30
Medium
8x8 XCaaS
8x8 XCaaS
$60 per seat per month
49
250 ms50%15
Medium
CloudTalk
CloudTalk
$25 – $50 /user/mo
47
23 ms40%500
Low
Synthflow AI
Synthflow AI
$0.08 /min (Growth)
20
2300 ms45%20
Low
Balto.ai
Balto.ai
$100 / seat /mo
12
100 ms0%40
High