It mainly depends what kind of games you play more often. Games can use both Open GL or Direct X for graphics. If a game says "NVidia The Way Games Are Meant To Be Played" or something like it when you load the game, then it is using Open GL. NVidia has been working their graphics cards with Open GL, so they are more powerfull when it comes to Open GL. ATI graphics cards, on the other hand, rule when it comes to Direct X. If you have alot of money to spend on our PC and are a hardcore PC gamer, it would be best to buy to graphics cards and a monitor switch to switch between video inputs. Also, a PCI Express video card works faster than regular AGP cards or older PCI cards.
