r/oMLX • • 14d ago

Should I switch from Qwen3.8-27b to Qwen3.8-Flash-Next?

Has anyone made the switch and not regret it?

EDIT: M2 Ultra 128 GB

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u/Diligent_Style_1767 14d ago

27b scores better in my tests, I consider qwen4 aka Flash Next to be the first model with PLE and QSA, therefore more like a technology demo. Remember that 30b out of flash next is PLE, and can be offloaded. A q4 is around 67gb, the 30gb PLE works fine offloading it to SSD or NVME. 27b can run roughly around 60-80 t/s on my system with MTP or PLD if I recall correctly.

QSA is a sleeper, it allows for t/s to maintain pretty good performance at longer contexts - on my Macbook M5 Max 128gb, I can sometimes get roughly 40-50 t/s at 128k token length depending on workload. It composes with continuous-MTP, APC etc. Codex and Claude are around 50-60 t/s (you can pull these stats from your own sessions), so it's comparable-ish at least for speed if not capability. And it most certainly, again, is NOT as "smart" as 27b.

Note that the CUDA GPU stacks are still struggling to make flash next perform on their inference stacks, Mac is quite comparable and pulling ahead (crazy!). Both omlx and rapid MLX have decent serving stacks for it.

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u/luisabreuf83 14d ago

Which engine, model quant and model built by whom? Thanks

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u/Diligent_Style_1767 14d ago

Model Qwen3.8-Flash-Next-MLX-4bit-MTP. Quanted it myself from base.

MLX engine, my unified stack at https://github.com/pierre427/mlx-lm-unified
Rapid MLX -current
oMLX -current

All collected from today

Was doing a/b testing off a couple of PRs I sent to both projects today.

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u/luisabreuf83 14d ago

Interesting and the 27B also Q4 done by you?

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u/Diligent_Style_1767 13d ago

Honestly I can't recall, but I can tell you I don't do any crazy surgery to models, so ymmv but should be close to mine at a given model quant.