Head-to-head comparison across 1benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.4 nano
59
Mellum2-12B-A2.5B-Instruct
27
Pick GPT-5.4 nano if you want the stronger benchmark profile. Mellum2-12B-A2.5B-Instruct only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.
Knowledge
+12.3 difference
GPT-5.4 nano
Mellum2-12B-A2.5B-Instruct
$0.2 / $1.25
N/A
191 t/s
N/A
3.64s
N/A
400K
128K
Pick GPT-5.4 nano if you want the stronger benchmark profile. Mellum2-12B-A2.5B-Instruct only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.
GPT-5.4 nano is clearly ahead on the provisional aggregate, 59 to 27. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.4 nano's sharpest advantage is in knowledge, where it averages 53.2 against 40.9. The single biggest benchmark swing on the page is GPQA, 82.8% to 40.9%.
GPT-5.4 nano is the reasoning model in the pair, while Mellum2-12B-A2.5B-Instruct is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. GPT-5.4 nano gives you the larger context window at 400K, compared with 128K for Mellum2-12B-A2.5B-Instruct.
GPT-5.4 nano is ahead on BenchLM's provisional leaderboard, 59 to 27. The biggest single separator in this matchup is GPQA, where the scores are 82.8% and 40.9%.
GPT-5.4 nano has the edge for knowledge tasks in this comparison, averaging 53.2 versus 40.9. Inside this category, GPQA is the benchmark that creates the most daylight between them.
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