Very interesting findings, thanks for sharing. I was facing exactly the same dilemma between these 2 cards, ended up staying with the 3080, just because was less expensive, although I like the AMD adrenalin interface. I’m still on a 1440p monitor, hoping to upgrade to 32’’ 4K in the near future.
When rendering at 4K both the 3080 and 6900 XT seemed identical. Perhaps because it was still a 1440p monitor, I couldn’t notice any difference in distant scenery textures, thought I admit I didn’t pay close attention.
I think the 3080 will be more than enough to keep until FS is upgraded to DX12. Then there will be benchmarks to assess which one is the better GPU.