Maximum PC

I can get the both for basically the same price, with the Geforce being 20$ more. I have a hard time overall deciding between Gefore or Radeon, but i mostly play games such Mass effect, the witcher, assassins creed 3 when it comes out. No fps games at all, nor competative multiplayer games. I will only use the one gpu, im not high on using dual cards or anything.

reviews for both cards:
http://www.techpowerup.com/reviews/Sapphire/HD_7950_Flex/1.html
http://www.anandtech.com/show/6159/the-geforce-gtx-660-ti-review

Its confusing with different sites having so different benchmark results.

Actually, there's no clear winner here. Relative performace wise, they are equals. Both cards are capable of driving all current games on a 30" LCD @ 2560x1600 with high quality settings & giving smooth game play throughout. Though some games like Metro 2033,Crysis: Warhead, Total War: Shogun 2 & some others are extremely demanding at maximum quality settings & will bring even these cards down to stuttering in some intense situations at 2560x1600, so they would need to be lowered to the "High Quality" setting for smooth gameplay.

Some games traditionally do better on Radeon cards & the 7950 will beat the 660Ti in all of those, other games traditionally do better on GeForce cards & the 660Ti will beat the 7950 in all of those. Then you have the grey area games where no chipset shows a clear advantage... in some of those the 7950 will win, in others, the 660Ti will win. But we're only talking 1 or 2 frames per second difference in these grey area games & maybe as much as 30-50% higher frame rates on a few select games that show a clear advantage for a particular chipset like Portal 2 with SSAA enabled or Crysis Warhead, though on most it will only be a couple percent difference.

Personally, I would go with the 660Ti for 4 reasons: but you'll have to evaluate the games you're playing and/or interested in then come to your own decision.
1> most of the games I am playing typically perform better on nVidia GPU's & for the rest, the 660Ti is only about 1% behind in frame rates.
2> 660Ti has a clear advantage in the power consumption department. By as much as 60 Watts less power in some games.
3> nVidia GPU's still perform better when running Folding @ Home.
4> That particular Gigabyte card is a known "best-of-the-best" card holding the GPU trifecta... high performance, low noise, low temperature.

Also if we take a look at a comparison, for the most part, the two cards are neck and neck in terms of performance. There are some tests that the Radeon HD smokes the GeForce, but keep in mind that the GeForce 600 series was meant to be a gaming GPU from the get go. The HD 7000 series was meant to be a "do everything" GPU.

But over all, yes, I agree with chaosdm. There are subtleties that get overlooked where the GTX 660 wins: power consumption, temperature, and noise.

What games are you usually playing chaosdm? Power consumption is definitely (note that it is spelled correctly) lower on the geforce, however noise levels are lower on this particular radeon board. Its the performance that is my key area. I usually play rpgs and action/adventure games.

Performance bias to a video card tends to depend on its engine. Unreal Engine has NVIDIA bias, and many games released these days use Unreal Engine. CryEngine 3 tends to have more preference for AMD I believe, but neither beat the snot out of each other. Frostbite 2 is GPU agnostic. Others tend to float here or there.

If it's an OpenGL application though, NVIDIA historically beat ATI/AMD. I'm not sure if this is the case still as OGL is somewhat of a footnote in modern gaming.

Do I want AMD to survive? Yes. Does that mean my preference for hardware is now them? No. My values for purchasing hardware are going to remain: who does better for the price? Not "who needs my money right now?"

Or rather, I don't want there to be an Intel/NVIDIA monopoly. Even if AMD fails, I'd rather their divisions be sold off to and actually capitalized by whoever buys them. Especially their CPU department. Yes they're at the mercy of Intel, but nobody uses Intel's latest and greatest when it comes out. Someone like Cyrix needs to come back... only they need to last for more than a generation.

they didnt go anywhere, they merged with national semiconductor, they made good co-processors, but were a bit slow compared to amd and Intel. had piss poor marketing as well. I have owned all of the processors up to the 586s, and some of the co-processors from the 286 and 386 eras. they never could sell to a big manufacturer, and ended up in the upgrade market. I guess they did ok considering they were texas instrument engineers.

Currently installed & played (at 1920x1200) within the last month: Skyrim, Deus Ex: Human Revolution, Diablo III, Battlefield 3, Batman: Arkham City, and Dragon Age II. Just finished DE:HR (2nd time around) & mostly Playing Skyrim right now & looking hard at Far Cry 3 as my potential next game.

BTW... Gaming resolution should also be considered when weighing the purchase options. The memory bus on the 660Ti favors 2.07MP (1920x1080) or lower resolutions, while the wider memory bus on the Radeon favors higher resolutions. So even in games where an overclocked 660Ti at 1680x1050 can match blows with the reference 7970 (Dragon Age II for example which loves nVidia cards) and runs about 18% faster than the reference 7950, at 2560x1600 that 7950 closes that gap to just 10%.