At higher resolutions and when you crank up AA in certain games you may want to have more than 2GB but for the most part it's fine.
The 760 is said to be a little bit faster than the 7950 but you have to consider what games you will be playing because in some games AMD cards are faster than Nvidia cards and visa versa.
Thing is though, most of the 7950/7970 card are sold out right now. The few that are available are way overpriced.
If you can come up with a little extra cash, I would get a GTX 770. It's more powerful than either of those cards and priced very reasonably right now.