Qwen3.5-27B vs Qwen3.5 397B

Pick Qwen3.5 397B if you want the stronger benchmark profile. Qwen3.5-27B only becomes the better choice if knowledge is the priority or you want the cheaper token bill.

Qwen3.5 397B finishes one point ahead on BenchLM's provisional leaderboard, 64 to 63. That is enough to call, but not enough to treat as a blowout. This matchup comes down to a few meaningful edges rather than one model dominating the board.

Qwen3.5 397B's sharpest advantage is in agentic, where it averages 56.2 against 51.6. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 41.6% to 52.5%. Qwen3.5-27B does hit back in knowledge, so the answer changes if that is the part of the workload you care about most.

Qwen3.5 397B is also the more expensive model on tokens at $0.60 input / $3.60 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for Qwen3.5-27B. That is roughly Infinityx on output cost alone. Qwen3.5-27B is the reasoning model in the pair, while Qwen3.5 397B 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. Qwen3.5-27B gives you the larger context window at 262K, compared with 128K for Qwen3.5 397B.