GLM-5.2 vs GPT-5.6 Luna
Head-to-head technical comparison of intelligence, capabilities, and API pricing.
Which should you use?
GLM-5.2 and GPT-5.6 Luna score within 0.5 points of each other on the composite index, which is too close to call a winner on capability alone.
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: GLM-5.2 is 7x the input price of GPT-5.6 Luna ($1.4 against $0.2 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
- Open weights, so it is the only one of the two you can run on your own hardware or keep data entirely in-house.
Pick GPT-5.6 Luna when
- Stronger on MMLU-Pro: 92% against 91.2%.
- Cheaper input tokens — $0.2 against $1.4 per 1M, so GLM-5.2 costs 7x as much to feed.
- Better value per point of measured capability: $0.002 per index point against $0.015.
Value per point of measured capability, at list input pricing: GPT-5.6 Luna $0.002 · GLM-5.2 $0.015 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.
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