GPT Realtime
- Strength
- Second-fastest response at 1.58s with 95.53% infrastructure-clean calls.
- What can be improved
- In a noisy-audio run, a long pause was followed by lost digits and a skipped tool action.
Speech-to-speech setup
- gpt-realtime-2.1
All platform comparisons
GPT Realtime · ranked 5 of 8Vapi · ranked 7 of 8
GPT Realtime vs Vapi
GPT Realtime 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 GPT Realtime for reliability across repeated runs (4.87 points higher), calls that connect and stay up (12.60 points higher), accurate tool calls (0.77 higher), how the agent sounds (0.17 higher), handling interruptions (0.25 higher) and fast replies (1.50s faster). Pick Vapi for completing the caller's task (4.88 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.
- GPT Realtime
- 64.63%5th
- Vapi
- 59.76%7th
GPT Realtime, 4.87 points higher
Task completion
Calls where the expected outcome was fully reached.
- GPT Realtime
- 92.68%6th
- Vapi
- 97.56%1st
Vapi, 4.88 points higher
Infrastructure-clean calls
Calls with no connection, audio or platform failure.
- GPT Realtime
- 95.53%6th
- Vapi
- 82.93%7th
GPT Realtime, 12.60 points higher
Tool call accuracy
Mean score for calling the right tool with the right arguments.
- GPT Realtime
- 4.79/52nd
- Vapi
- 4.02/58th
GPT Realtime, 0.77 higher
Voice tone and clarity
Mean score for how clear and natural the agent sounds.
- GPT Realtime
- 4.25/54th
- Vapi
- 4.08/56th
GPT Realtime, 0.17 higher
Interruption handling
Mean score for yielding and recovering when the caller cuts in.
- GPT Realtime
- 4.98/52nd
- Vapi
- 4.73/57th
GPT Realtime, 0.25 higher
Mean response time
Mean time for the agent to start replying after the caller stops.
- GPT Realtime
- 1.58s2nd
- Vapi
- 3.08s8th
GPT Realtime, 1.50s 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 GPT Realtime or Vapi more reliable?
GPT Realtime is more reliable, by 4.87 points. GPT Realtime passed 64.63% 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, GPT Realtime or Vapi?
GPT Realtime starts replying sooner, 1.50s faster. Mean response time is 1.58s for GPT Realtime and 3.08s for Vapi.
Which completes more calls, GPT Realtime or Vapi?
GPT Realtime reached the expected outcome on 92.68% of calls and Vapi on 97.56%. Vapi is ahead on task completion.
How were GPT Realtime 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.