Honestly can’t say I’ve noticed all that much!
You probably don’t have wide feet then :-p
In terms of width I found:
Fizik -> Shimano, Northave & Sidi (all subtly different, SIDI almost fit me despite not being ‘wide’) -> Bontranger -> Specialized -> Shimano Wide fit
Shimano wide is is really wide, probably too wide, but the only thing that I can get my feet in so I put up with the slightly baggy fit.
Fizik were by far the nicest shoes, they just didn’t get anywhere near fitting. That said, shimano obviously use different molds for their MTB shoes as they’re mostly fine.