Grok 4.6 vs Gemini 3.1 Ultra
Head-to-head technical comparison of intelligence, capabilities, and API pricing.
Which should you use?
Grok 4.6 leads on the composite index by 1.3 points (93.8 vs 92.5).
Their Arena Elo differs by only 10 points, inside the confidence intervals the public board reports, so human preference does not separate them.
Cost is the sharper difference: Gemini 3.1 Ultra is 10x the input price of Grok 4.6 ($20 against $2 per 1M), so at volume the choice is usually decided by budget rather than benchmarks.
Pick Grok 4.6 when
- Higher composite index — 93.8 against 92.5, a gap of 1.3 points.
- Stronger on MMLU-Pro: 93.1% against 92.5%.
- Cheaper input tokens — $2 against $20 per 1M, so Gemini 3.1 Ultra costs 10x as much to feed.
- Better value per point of measured capability: $0.021 per index point against $0.216.
Pick Gemini 3.1 Ultra when
On these measures Gemini 3.1 Ultra does not lead Grok 4.6 anywhere, so pick it only for reasons outside this table — an existing integration, a region, or a contract.
Value per point of measured capability, at list input pricing: Grok 4.6 $0.021 · Gemini 3.1 Ultra $0.216 per index point. Run your own token mix through the token cost calculator — a comparison at list price ignores caching and batch discounts, which move real bills more than this gap does.
Where these numbers come from
Figures as of 2026-09-07. Arena Elo and pricing are read from the public board and each vendor's own pricing page; see the full leaderboard for all 34 models and which columns are measured rather than estimated, or the benchmark matrix for scores benchmark by benchmark.