Head-to-head comparison across 3benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Mellum2-12B-A2.5B-Instruct
27
o3-mini
55
Pick o3-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.
Coding
+12.1 difference
Knowledge
+36.3 difference
Inst. Following
+18.1 difference
Mellum2-12B-A2.5B-Instruct
o3-mini
N/A
$1.1 / $4.4
N/A
160 t/s
N/A
7.12s
128K
200K
Pick o3-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.
o3-mini is clearly ahead on the provisional aggregate, 55 to 27. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
o3-mini's sharpest advantage is in knowledge, where it averages 77.2 against 40.9. The single biggest benchmark swing on the page is GPQA, 40.9% to 77.2%.
o3-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. o3-mini gives you the larger context window at 200K, compared with 128K for Mellum2-12B-A2.5B-Instruct.
o3-mini is ahead on BenchLM's provisional leaderboard, 55 to 27. The biggest single separator in this matchup is GPQA, where the scores are 40.9% and 77.2%.
o3-mini has the edge for knowledge tasks in this comparison, averaging 77.2 versus 40.9. Inside this category, GPQA is the benchmark that creates the most daylight between them.
o3-mini has the edge for coding in this comparison, averaging 49.3 versus 37.2. Mellum2-12B-A2.5B-Instruct stays close enough that the answer can still flip depending on your workload.
o3-mini has the edge for instruction following in this comparison, averaging 93.9 versus 75.8. Inside this category, IFEval is the benchmark that creates the most daylight between them.
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