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-Thinking
59
Treat this as a split decision. GPT-5.4 nano makes more sense if you need the larger 400K context window; Mellum2-12B-A2.5B-Thinking is the better fit if knowledge is the priority.
Knowledge
+4.4 difference
GPT-5.4 nano
Mellum2-12B-A2.5B-Thinking
$0.2 / $1.25
N/A
191 t/s
N/A
3.64s
N/A
400K
128K
Treat this as a split decision. GPT-5.4 nano makes more sense if you need the larger 400K context window; Mellum2-12B-A2.5B-Thinking is the better fit if knowledge is the priority.
GPT-5.4 nano and Mellum2-12B-A2.5B-Thinking finish on the same provisional overall score, so this is less about a single winner and more about where the edge shows up. The provisional headline says tie; the benchmark table is where the real choice happens.
GPT-5.4 nano gives you the larger context window at 400K, compared with 128K for Mellum2-12B-A2.5B-Thinking.
GPT-5.4 nano and Mellum2-12B-A2.5B-Thinking are tied on the provisional overall score, so the right pick depends on which category matters most for your use case.
Mellum2-12B-A2.5B-Thinking has the edge for knowledge tasks in this comparison, averaging 57.6 versus 53.2. Inside this category, GPQA is the benchmark that creates the most daylight between them.
For engineers, researchers, and the plain curious — a weekly brief on new models, ranking shifts, and pricing changes.
Free. No spam. Unsubscribe anytime.