Qwen3.5 9B sparks GGUF vs MLX debate

For this model, format choice matters less than whether you care about speed or predictability. The real quality gap is mostly about quantization level, with higher-bit GGUFs usually holding up best when you can afford the memory.

• –Official Qwen3.5-9B is a serious 9B-class model with 262k-token context, so it is worth treating as a real local workhorse rather than a toy
• –GGUF maintainers generally point to Q6_K or Q5_K_M as the quality sweet spot; Q4_K_M is the pragmatic default when memory is tighter
• –Apple Silicon users report MLX can be much faster than GGUF, but some Qwen3.5 MLX quants have shown odd thinking-loop behavior that GGUF avoids
• –On an M3 Pro, the practical recommendation is usually to try MLX first for speed, then fall back to GGUF Q5/Q6 if you want steadier behavior or higher fidelity