The 7950 will have a performance advantage in Battlefield 4 and future Frostbite engine games (Star Wars Battlefront, Dragon Age Inquisition, Need for Speed Rivals, Mirror's Edge 2, next Mass Effect) as well as better performance in resolutions beyond 1080p. It overclocks very well to match the performance of the 7970.
The GTX 760 is a better choice if you do video recording, streaming, encoding, 3D gaming. Or want to take advantage of proprietary Nvidia features like Physx and G-Sync.
And then both feature different free games.