The 6900XT is faster than the 3080 at every resolution.
It should cost more as well, but if it costs less for you, that's actually a good thing.
It's about 5-12% faster in everything but RTX, where it becomes even slower than the 3070.
I haven't heard any game changing bugs for the 6000 series, but from my experience with rx 400, 500, vega, and 5000, they usually have worse drivers than nvidia.