GLM-5.2 vs Gemini 3.1 Ultra
Head-to-head technical comparison of intelligence, capabilities, and API pricing.
Which should you use?
Gemini 3.1 Ultra leads on the composite index by 1 points (91.5 vs 92.5).
Cost is the sharper difference: Gemini 3.1 Ultra is 14.3x the input price of GLM-5.2 ($20 against $1.4 per 1M), so at volume the choice is usually decided by budget rather than benchmarks.
Only GLM-5.2 ships open weights, which decides it outright if the workload has to run on your own hardware.
Pick GLM-5.2 when
- Cheaper input tokens — $1.4 against $20 per 1M, so Gemini 3.1 Ultra costs 14.3x as much to feed.
- Open weights, so it is the only one of the two you can run on your own hardware or keep data entirely in-house.
- Better value per point of measured capability: $0.015 per index point against $0.216.
Pick Gemini 3.1 Ultra when
- Higher composite index — 92.5 against 91.5, a gap of 1 points.
- Ahead on Arena Elo by 15 points (1480 vs 1465), which is outside the board's published confidence intervals.
- Stronger on MMLU-Pro: 92.5% against 91.2%.
Value per point of measured capability, at list input pricing: GLM-5.2 $0.015 · 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 2026-09-14. 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.