The truth is actually just the opposite Nightmare. At least my experience with Nvidia cards tell me otherwise (had a Geforce 9500 back in the day too, wasn't an AMD fanboy always xD).
Well, it WAS just a joke anyways.
My opinion is that Nvidia has slightly higher quality standart, while amd bets on making their hardware affordable. Either way, you should really be okay with either of them.
Pick by color you like!