what's your indication that a 3080 is 20% faster than a 6800XT?I don't assume that because even AMD didn't show parity if you read between the lines. SAM / resizeable BAR is coming to Ampere too which makes that gain moot.
Raster/$ should end up around parity at MSRP, though Nvidia will have more total raster in the price tier.
VRAM/$ AMD will have more obviously.
Depends what your priorities are. I take 10-20% more raster at the sacrifice of 38% VRAM any day if I have a choice. But at this point I don't and will take 3080 or 6800XT whatever I can buy first.