Retell
- Strength
- Leads repeatable reliability at 75.61% pass³.
- What can be improved
- The transcript captured a phone number correctly, but a different number was sent to the tool.
STT, LLM and TTS
- accurate (Retell-managed STT)
- gpt-5.5
- eleven_flash_v2
All platform comparisons
Retell · ranked 1 of 8Vapi · ranked 7 of 8
Retell vs Vapi
Retell is ahead on repeatable reliability, infrastructure reliability, tool call accuracy, voice tone and clarity, interruption handling and response time, and Vapi on task completion.
Last updated Methodology by Luis Ojeda
Verdict
Which to pick
Pick Retell for reliability across repeated runs (15.85 points higher), calls that connect and stay up (15.44 points higher), accurate tool calls (0.82 higher), how the agent sounds (0.28 higher), handling interruptions (0.27 higher) and fast replies (0.87s faster). Pick Vapi for completing the caller's task (3.68 points higher).
Head to head
Every metric, side by side
Bars share one scale across all 8 platforms. The place next to each figure is its rank in the field.
Repeatable reliability
Share of the 82 scenarios that passed on all three runs.
- Retell
- 75.61%1st
- Vapi
- 59.76%7th
Retell, 15.85 points higher
Task completion
Calls where the expected outcome was fully reached.
- Retell
- 93.88%5th
- Vapi
- 97.56%1st
Vapi, 3.68 points higher
Infrastructure-clean calls
Calls with no connection, audio or platform failure.
- Retell
- 98.37%4th
- Vapi
- 82.93%7th
Retell, 15.44 points higher
Tool call accuracy
Mean score for calling the right tool with the right arguments.
- Retell
- 4.84/51st
- Vapi
- 4.02/58th
Retell, 0.82 higher
Voice tone and clarity
Mean score for how clear and natural the agent sounds.
- Retell
- 4.36/52nd
- Vapi
- 4.08/56th
Retell, 0.28 higher
Interruption handling
Mean score for yielding and recovering when the caller cuts in.
- Retell
- 5.00/51st
- Vapi
- 4.73/57th
Retell, 0.27 higher
Mean response time
Mean time for the agent to start replying after the caller stops.
- Retell
- 2.21s5th
- Vapi
- 3.08s8th
Retell, 0.87s faster
246 calls per platform: 82 scenarios, 3 runs each.
On the calls
What each platform ran, and what we saw
Vapi
- Strength
- Tied for first in task completion at 97.56% across 205 calls with outcome evidence.
- What can be improved
- The remaining 41 of 246 calls did not connect and remain visible in infrastructure reliability.
STT, LLM and TTS
- stt-rt-v5
- gpt-4.1-2025-04-14
- vapi-v2 (Clara)
Frequently asked questions
Is Retell or Vapi more reliable?
Retell is more reliable, by 15.85 points. Retell passed 75.61% of the 82 scenarios on all 3 runs and Vapi passed 59.76%. A scenario only counts when every run of it passed.
Which responds faster, Retell or Vapi?
Retell starts replying sooner, 0.87s faster. Mean response time is 2.21s for Retell and 3.08s for Vapi.
Which completes more calls, Retell or Vapi?
Retell reached the expected outcome on 93.88% of calls and Vapi on 97.56%. Vapi is ahead on task completion.
How were Retell and Vapi tested?
Both ran the same Appointment and Medicare agents through the same 82 caller scenarios, 3 times each, with the same evaluators and mock tools. Only the platform and its speech and model components changed.