I'm gonna go ahead and get this out of the way, it really doesn't matter, you can hardly find any differences between like cards between the two companies. As far as who has THE best one it all depends on who has the best card at this second in time, right now I guess it's the x1900xt, before it was the 7800gtx, in a little while it'll probably be the 7900whatever, it's a constant cycle. You really can't go wrong either way, just choose what fits your budget, and search for benchmarks between two cards if you're stuck between them