All comes down to the price. 6800xt would be good if it was actually cheaper than the 3080.
If we're talking top tier AIB on both sides, the Sapphire Nitro 6800xt would be good value. But it's a lot tougher to decide when a Sapphire Nitro 6800xt (among the AMD top tier) and a MSI Ventus 3080 (fairly average, or even lower tier Nvidia AIB) had local srps of 1259 and 1209 respectively.
I was a long-time AMD user who made the switch to Nvidia this gen, which I think was a good choice in retrospect. When I was using AMD, I didn't really miss the features they lacked, but there were always compromises here and there; like really poor OpenGL performance, crappy x264 hardware encoding.
I look forward to trying out AMD cards again one day, but I'm enjoying the Nvidia features so far.