i ill go for nvidia i hate having driver issues and if u have intel cpu u should get nvidia

I'm a bitch for NVIDIA, so I can't very well give any kind of unbiased opinion here. I'll just move along.

get the GTX680

Most games are optimized for Nvidia and CUDA is used more often. Also much games are using physx which works better on NVidia

I'd say go for Nvidia too, but there are just a handful of good games that use Physx, I wouldn't say that should be any choosing point. Games coming up that use it are Metro Last Ligth, Borderlands 2 and ArmA 3, so yeah, don't see Physx as a sellig point, but I would get the Nvidia 6 series, 670/680.

I have had very bad experiences with multiple Nvidia cards which were only solved when I switched over to AMD. Back in the day, ATI's drivers were loathsome and Nvidia's were better, but this is no longer the same. Nvidia's drivers frequently caused BSODs while gaming in multiple builds my brother and I had, and these issues persisted over the years despite our using 5 different cards of theirs (5200, 5500, 6200, 7600GT, GTX275) and several versions of their drivers. On the other hand, AMD's drivers get the job done without any kind of complication, I yet have to experience an issue while using them.

tl;dr - Get AMD, it's safer.

Consider buying GTX680 from MSI. IMHO it has the coolest cooling system around. And, of course, NO to 7970. Nvidia FTW!!!1

DON'T FALL FOR THE SHIT THAT IS ATI/AMD!

Nvidia all the way!

Personally, I have two 7970s in crossfire. When they work, they are absolutely wonderful.
When they work.
They are terrific cards, killed by the drivers. Apparently, running them in crossfire mode with multiple monitors makes the drivers not so happy. Since there isn't much reason for one without the other, it seems a bit silly that this particular scenario is broken more often than not. (I oftentimes get better frame rates without the crossfire...)
I've used every version of the drivers released since the cards came out, and each version fixes one thing while breaking another.
I'm switching to a pair of either 680s or 670s, as soon as I can find some of them with 4G available.

Nvida is better for gaming because they pay more to the developers :)