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 8Retell · ranked 1 of 8
GPT Realtime vs Retell
Retell is ahead on repeatable reliability, task completion, infrastructure reliability, tool call accuracy, voice tone and clarity and interruption handling, and GPT Realtime on response time.
Last updated Methodology by Luis Ojeda
Verdict
Which to pick
Pick GPT Realtime for fast replies (0.63s faster). Pick Retell for reliability across repeated runs (10.98 points higher), completing the caller's task (1.20 points higher), calls that connect and stay up (2.84 points higher), accurate tool calls (0.05 higher), how the agent sounds (0.11 higher) and handling interruptions (0.02 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
- Retell
- 75.61%1st
Retell, 10.98 points higher
Task completion
Calls where the expected outcome was fully reached.
- GPT Realtime
- 92.68%6th
- Retell
- 93.88%5th
Retell, 1.20 points higher
Infrastructure-clean calls
Calls with no connection, audio or platform failure.
- GPT Realtime
- 95.53%6th
- Retell
- 98.37%4th
Retell, 2.84 points higher
Tool call accuracy
Mean score for calling the right tool with the right arguments.
- GPT Realtime
- 4.79/52nd
- Retell
- 4.84/51st
Retell, 0.05 higher
Voice tone and clarity
Mean score for how clear and natural the agent sounds.
- GPT Realtime
- 4.25/54th
- Retell
- 4.36/52nd
Retell, 0.11 higher
Interruption handling
Mean score for yielding and recovering when the caller cuts in.
- GPT Realtime
- 4.98/52nd
- Retell
- 5.00/51st
Retell, 0.02 higher
Mean response time
Mean time for the agent to start replying after the caller stops.
- GPT Realtime
- 1.58s2nd
- Retell
- 2.21s5th
GPT Realtime, 0.63s faster
246 calls per platform: 82 scenarios, 3 runs each.
On the calls
What each platform ran, and what we saw
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
Frequently asked questions
Is GPT Realtime or Retell more reliable?
Retell is more reliable, by 10.98 points. GPT Realtime passed 64.63% of the 82 scenarios on all 3 runs and Retell passed 75.61%. A scenario only counts when every run of it passed.
Which responds faster, GPT Realtime or Retell?
GPT Realtime starts replying sooner, 0.63s faster. Mean response time is 1.58s for GPT Realtime and 2.21s for Retell.
Which completes more calls, GPT Realtime or Retell?
GPT Realtime reached the expected outcome on 92.68% of calls and Retell on 93.88%. Retell is ahead on task completion.
How were GPT Realtime and Retell 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.