Generally speaking the Intel CPU is better at performing several tasks than an AMD cpu on a like for like core count and Ghz comparison. However the AMD does come at a better price point and is often more readily overclocked.
Between ATI and Nvidia it's really not that different. Personally I would say Nvidia but this is an age old argument that will likely never be settled. The reason I state Nvidia is because there driver team are always on the ball, making optimisations for the latest games, However recently the AMD drivers have been coming along better than they used to. Also if you really want to blow your wallet get your GPU from EVGA.