Cozzo-tested · Oct 20, 2026
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Vapi vs Ultravox: tested on real phone calls
On our phone calls, Ultravox replied faster: a 1.18 s median versus 1.56 s for Vapi, a gap of 0.38 s.
Reply time is the gap from the end of the caller’s speech to the agent’s first reply audio, timed from our recording of real phone calls (Twilio calling each vendor from a US number, Ashburn, Virginia (US East)), on each vendor’s default model and voice, with the same short dental-receptionist script. Twilio added about $0.01/min for the phone leg (SIP dial-out plus recording). Small samples: differences of a few hundredths of a second are noise. Ranking order comes only from the measured medians.
Vapi
Vapi’s $0.05/min hosting plus pass-through model, transcription and voice charges.
One reply began 0.26 s before the caller audio ended.
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Ultravox
Most of our Ultravox time used its free minutes; the rest is billed at $0.05/min. The total also covers Ultravox acting as our scripted caller, and is our calculation from billed seconds (Ultravox shows no dollar usage).
- Full phone-call benchmark: all 8 platforms, method and limits.
- Ultravox vs Vapi: pricing and features side by side, with a cost-at-volume calculator.
- Methodology and how we test.
Other head-to-heads
Cozzo may earn a commission if you sign up through some links. It never affects our rankings or test results.