Verdict
Built from the measurements below
- Accuracy is too close to call: Gemini 3.1 Pro Preview scored 77.5% and Grok 4.7 80.0% on the same 80 questions, a gap within what chance alone could produce.
- Gemini 3.1 Pro Preview is 1.5× cheaper per question as billed ($0.017 vs $0.025), reasoning tokens included.
- Gemini 3.1 Pro Preview generates text 1.6× faster: 124 tokens per second against 77.
- Grok 4.7 starts answering sooner: 1.9 s to the first token, against 3.4 s for Gemini 3.1 Pro Preview.
- Gemini 3.1 Pro Preview accepts more context: 1M tokens against 500k.
Which should you choose?
Choose Gemini 3.1 Pro Preview for the lower cost per correct answer ($0.022 against $0.031), faster streaming, shorter outputs (about 1,382 tokens per question against 3,952) and a 1M-token context window. Choose Grok 4.7 for a quicker first token.
Accuracy gap -2.5 points (z = -0.39). We call a winner only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.