If you don't want an AMD card, then don't get one. You shouldn't let a few FPS in certain games be your deciding factor. These cards are essentially the same, maybe there's an insignificant advantage for the 7970 GHz in a few games, but that also applies to the GTX 680 (Assassin's Creed, Borderlands 2, Call of Duty: Black Ops 2, Skyrim, Bioshock Infinite, Crysis 3, etc.).
http://www.techpowerup.com/reviews/ASUS/GeForce_GTX_670_Direct_Cu_Mini/7.html
http://www.guru3d.com/articles_pages/evga_geforce_gtx_650_ti_boost_sc_review,13.html
On the other hand, there are some definite advantages for the GTX 680 that tend to get missed when you just take a simple view on FPS averages. The two big ones are unique technologies and driver support.
- For me, and I know the AMD fans hate this, but I wouldn't buy a card that can't do PhysX or Adaptive VSync. With all else equal, it makes no sense to get a card that doesn't have them. I use them and would not want to go without them. There's enough good PhysX games out now and coming out to make it likely you will be running at least one PhysX game, and that's all it takes.
- The GTX 680 will have better driver support for newer games. This was especially obvious for BF3 and will most certainly be the case with BF4. There was also a recent series of articles that exposed excessive stuttering in AMD cards just a couple months ago. AMD came out with a partial fix that applied to specific games, but still.
http://www.hardocp.com/article/2013/03/04/2012_amd_nvidia_driver_performance_summary_review/5
http://techreport.com/review/23981/radeon-hd-7950-vs-geforce-gtx-660-ti-revisited