well a) if the only choice i had was between those two cards which would be btter....and b) would this card suffice? Sapphire Radeon HD 7950 3GB DDR5 HDMI/DVI-I/Dual Mini DisplayPort PCI-Express Graphics Card with Boost 21196-00-20G
The GTX 660 Ti is the better of the two (in your original post), although its just academic considering its 1680x1050. For no more resolution than that you might as well just get a GTX 650 Ti Boost. An HD 7950 or GTX 660 Ti would be a waste.
then you have to buy another graphics card because a 256 bit memory interface will never push that much data but with the 7950 you can always add more and push those resolutions. you can stick a 7990 on top of the 7950 if needed. i like the 386 bit memory interface, but people still buy into the same memory interface i had on my old gtx 560. I am no fanboy just a man who does not like to spend money on old tech.
the 660ti is a 192 bit memory interface i beleive, not even good enough for max settings at 1080p.