Qwen is better at some things (code, in particular), but Gemma has better prose and better vision. At least, it feels that way to me.
best is to use your own model router atm, depending on the task
I haven't yet compared either to Gemma 4. I tried that out the day after it came out with the patched llama.cpp that added support for it but I couldn't make tool calling work and so it was kind of useless. I should try again to see if things have changed but judging by what people say, qwen-3.6 seems stronger for coding anyway.