> I prefer fixed width

Do you have examples for problems that are easier to solve in fixed-width SIMD?

I maintain that most problems can be solved in a vector-length-agnostic manner. Even if it's slightly more tricky, it's certainly easier than restructuring all of your memory allocations to add padding and implementing three versions for all the differently sized SIMD extensions your target may support. And you can always fall back to using a variable-width SIMD ISA in a fixed-width way, when necessary.