Head-to-head comparison across 1benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.4 mini
69
Mellum2-12B-A2.5B-Instruct
27
Pick GPT-5.4 mini 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
+16.5 difference
GPT-5.4 mini
Mellum2-12B-A2.5B-Instruct
$0.75 / $4.5
N/A
201 t/s
N/A
3.85s
N/A
400K
128K
Pick GPT-5.4 mini 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 mini is clearly ahead on the provisional aggregate, 69 to 27. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.4 mini's sharpest advantage is in knowledge, where it averages 57.4 against 40.9. The single biggest benchmark swing on the page is GPQA, 88% to 40.9%.
GPT-5.4 mini 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 mini gives you the larger context window at 400K, compared with 128K for Mellum2-12B-A2.5B-Instruct.
GPT-5.4 mini is ahead on BenchLM's provisional leaderboard, 69 to 27. The biggest single separator in this matchup is GPQA, where the scores are 88% and 40.9%.
GPT-5.4 mini has the edge for knowledge tasks in this comparison, averaging 57.4 versus 40.9. Inside this category, GPQA is the benchmark that creates the most daylight between them.
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