Arguement of 7950 and 660 Ti has been asked for a quite a few times recently.
660 Ti is better when you want to play a game with 1920x1080 with kind of a lower settings, because of the lower bus bandwidth. And it is more efficient.
But if you want to crank up the AA you better get a 7950. And, if you want to do something aside from gaming like OpenCL rendering go with the 7950. The 660 Ti lacks in that division.
I would go for these instead:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202006
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121656