RTX 3090 vs RTX 4080?

I'm looking to transition from paid chat gpt to local ai for better private data access and use.

Both cards are comparable in price (around $1000 currently). 4080 is obviously better as a graphics card but I'm not finding a clear answer on how they compare for AI given that the 3090 has more VRAM. Can anybody offer guidance on which to buy?

What is the best model(s) a card like this could run currently?