I can say that in Cyberpunk 2077 with Ultra Ray Tracing (+Psycho RT lighting) I haven't seen any signs of running out of memory on my 3080. I've seen allocation get up to 95% but none of the telltale hitches that would suggest actually running out of vram.

When I was shopping and doing my research I considering the 6800XT and 3080 to be basically dead even. After getting the 3080 and actually using the extra features (better RT, DLSS) I wouldn't even consider the 6800XT anymore. I think the 6800XT needs to be more like $75-100 less than the 3080 (and it's ridiculous that I've seen 6800XT going for more than the 3080!).

If you're talking 3070 or 3060 Ti vs the AMD equivalents then I would be more inclined to go with AMD as those aren't quite as able to do the ray tracing.

Finally I will just that it is absolutely imperative that AMD gets a DLSS competitor/equivalent out as soon as possible. After using the tech in person it more than lives up to the hype so the only thing holding it back is widescale adoption. If DLSS makes its way into all the big new releases from here on out (and any developer would be crazy to not get it in their game, imo) then AMD is going to get buried.