Head-to-head comparison across 2benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Sonnet 4.6
83
Mellum2-12B-A2.5B-Thinking
59
Pick Claude Sonnet 4.6 if you want the stronger benchmark profile. Mellum2-12B-A2.5B-Thinking only becomes the better choice if coding is the priority or you want the stronger reasoning-first profile.
Coding
+3.5 difference
Knowledge
+16.1 difference
Claude Sonnet 4.6
Mellum2-12B-A2.5B-Thinking
$3 / $15
N/A
44 t/s
N/A
1.48s
N/A
200K
128K
Pick Claude Sonnet 4.6 if you want the stronger benchmark profile. Mellum2-12B-A2.5B-Thinking only becomes the better choice if coding is the priority or you want the stronger reasoning-first profile.
Claude Sonnet 4.6 is clearly ahead on the provisional aggregate, 83 to 59. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Claude Sonnet 4.6's sharpest advantage is in knowledge, where it averages 73.7 against 57.6. The single biggest benchmark swing on the page is GPQA, 89.9% to 57.6%. Mellum2-12B-A2.5B-Thinking does hit back in coding, so the answer changes if that is the part of the workload you care about most.
Mellum2-12B-A2.5B-Thinking is the reasoning model in the pair, while Claude Sonnet 4.6 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. Claude Sonnet 4.6 gives you the larger context window at 200K, compared with 128K for Mellum2-12B-A2.5B-Thinking.
Claude Sonnet 4.6 is ahead on BenchLM's provisional leaderboard, 83 to 59. The biggest single separator in this matchup is GPQA, where the scores are 89.9% and 57.6%.
Claude Sonnet 4.6 has the edge for knowledge tasks in this comparison, averaging 73.7 versus 57.6. Inside this category, GPQA is the benchmark that creates the most daylight between them.
Mellum2-12B-A2.5B-Thinking has the edge for coding in this comparison, averaging 69.9 versus 66.4. Claude Sonnet 4.6 stays close enough that the answer can still flip depending on your workload.
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