Mistral Small 3 and GPT-5 nano don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Mistral Small 3 shipped 218 days before GPT-5 nano, so benchmark comparisons should account for the intervening progress.

Mistral Small 3 is open weight, while GPT-5 nano is proprietary.

Direct benchmark comparisons are unavailable — Mistral Small 3 and GPT-5 nano don't publish scores on any of the same benchmarks.