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Gemini 3.1 Flash Live Preview vs Grok Voice Think Fast 2.0

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Gemini 3.1 Flash Live PreviewGoogle
Wins 4 of 8
Reliability
62.2%
Response time
2.88s
Cost / min
$0.0703
Grok Voice Think Fast 2.0xAI
Wins 3 of 8
Reliability
67.1%
Response time
1.62s
Cost / min
$0.0800

Gemini 3.1 Flash Live Preview is ahead on data accuracy, calls where the agent went quiet, interruption and cost, and Grok Voice Think Fast 2.0 on reliability, agent responses and response time. The two tie on success rate.

Last updated Methodology by Dileep Chagam

Who is better at what

For the wider field, see our pick of the best voice AI APIs for real-time audio.

Gemini 3.1 Flash Live PreviewGrok Voice Think Fast 2.0
  • Reliability62.2%67.1%
  • Success rate76.0%76.0%
  • Agent responses95.9%96.7%
  • Data accuracy79.2%78.9%
  • Went quiet3.3%4.5%
  • Interruption4.984.92
  • Response time2.88s1.62s
  • Cost / min$0.0703$0.0800

Reliability on booking and Medicare calls

Scenarios the agent passed on every one of its 3 runs.

Booking callsMedicare calls
  1. 83%
    9%
    Gemini 3.1 Flash Live Preview
  2. 92%
    4%
    Grok Voice Think Fast 2.0

Related comparisons

Both providers, every model: Google vs xAI

Each model on its own: Gemini 3.1 Flash Live Preview and Grok Voice Think Fast 2.0

Gemini 3.1 Flash Live Preview vs Grok Voice Think Fast 2.0 FAQ

  • Grok Voice Think Fast 2.0 is more reliable, by 4.9 points. Gemini 3.1 Flash Live Preview passed 51 of 82 scenarios on all three runs, and Grok Voice Think Fast 2.0 passed 55. A scenario only counts when every run of it passed.

  • For a voice agent, Grok Voice Think Fast 2.0, since it gets more scenarios right on every run. Gemini 3.1 Flash Live Preview is ahead on data accuracy, calls where the agent went quiet, interruption and cost, and Grok Voice Think Fast 2.0 on reliability, agent responses and response time. The two tie on success rate.

  • Gemini 3.1 Flash Live Preview, by 0.3 points. Gemini 3.1 Flash Live Preview saved everything exactly right on 79.2% of the calls that save data, and Grok Voice Think Fast 2.0 on 78.9%. On Booking calls, 96.5% against 97.1%. On Medicare calls, 34.8% against 31.8%. A call counts only when nothing is missing, wrong, extra or saved twice.

  • No. Grok Voice Think Fast 2.0 starts replying 1.26s sooner at the median. Gemini 3.1 Flash Live Preview takes 2.88s at the median and 4.00s at p90; Grok Voice Think Fast 2.0 takes 1.62s and 1.94s. Both are measured on the call audio, from the caller finishing to the agent starting to reply.

  • Gemini 3.1 Flash Live Preview, by 0.06 on a 0 to 5 scale. Gemini 3.1 Flash Live Preview scores 4.98 and Grok Voice Think Fast 2.0 4.92 for how well the agent handled being talked over.

  • Gemini 3.1 Flash Live Preview, by 1.2 points. The agent went quiet for 10 seconds or more on 3.3% of Gemini 3.1 Flash Live Preview calls and 4.5% of Grok Voice Think Fast 2.0 calls.

  • Gemini 3.1 Flash Live Preview is $0.0097 cheaper a minute. Gemini 3.1 Flash Live Preview costs $0.0703 a minute of call and Grok Voice Think Fast 2.0 $0.0800, at each vendor's published rates.

  • Cekura ran both as the whole agent in the same open-source Pipecat pipeline, with the same prompt, tools and connection. A simulated caller worked through all 82 scenarios on live calls, three times each, 3,690 calls across the benchmark. A call passes only when the agent said the right things and saved the right data.

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