I myself have always sticked with nvidia. Ive always heard that ati cards dont overheat good, and the fans break down more often...
I also cant stand that stupid catalyist control system, or what ever the h*** its called.
I myself would go for the 260... or wait for the next gen of nvidia cards that will come out in acouple of months. (they will support DX 10.1, and maby if were lucky DX 11.)
my 2c...