the difference between current AMD and Nvidia GPUs isn't even that large if viewed from price/performance ratio...
Comparing cards at similar price has AMD having slightly less performance while having significantly more GDDR memory.
i still use an RTX3080 though, thankfully got one before the current craze started
The difference between AMD and Nvidia is _huge_ when you look at software support and drivers and etc. Part of this is network effects and part of it is just AMD itself. But the hard reality is I'd never buy AMD for compute, even if in specs it were better.
Just as a random anecdote, I grabbed an AMD 5700xt around when those came out (for gaming). Since I had it sitting around between gaming sessions, I figured I'd try to use it for some compute, for Go AI training. For _1.5 years_ there existed a showstopping bug with this, it just could not function for all of that time. They _still_ do not support this card in their ROCm library platform last I checked. The focus and support from AMD is just not there.
i still use an RTX3080 though, thankfully got one before the current craze started