I have always believed Nvidia to be the best for FPS games becuase they tended to send more of their programmers / designers into game developing houses such as DICE etc.
These Nvidia developers worked with the game designers to help ensure they got the most out of the current GPU's supplied by Nvidia and that the drivers and the card worked well the game.
ATI historically have done this far less but have recently realised it is the way forward and are catching up as regards the amount of their people going into these game development houses and working with them.
Realising ATI were upping their game was one of the things I considered when buying this card as I wanted the best compatibility possible.
Also in the past my fellow clan mates have been crashing and burning left right and center, most of the time they were the ones using ATI cards.
My Nvidia GPU using clan mates had far less problems on average.
This is why I had allegiance to NVidia