Every single person pimping for the 270X on this thread has touted BF3/BF4 numbers without looking at how the cards perform in other games. I don't think that's reasonable.
GTX 760 with free game vs 270X with no free game, we'll say that's about even on price.
As for performance the 760 is 12% faster in all games overall at 1080p, per TechPowerUp.
Even in BF3 and BF4 it's faster, and if OP ever wants to play anything else, he'll have that 12% margin. Possibly more if you compare overclock vs overclock since the GTX 760 starts off at a higher base speed.
As for those saying 'well OP mentioned BF4' or whatever, please note OP also mentioned BF3, and I doubt he wants to play only BF3/4 forever so the GTX 760's ~12% average advantage over
BF3, the GTX 760 easily beats the 270X, 70.3 fps vs 55 fps:
http://www.anandtech.com/show/7503/the-amd-radeon-r9-270x-270-review-feat-asus-his/8
BF4 tests generally show the GTX 760 basically tied with the R9 270X if not faster:
http://www.techpowerup.com/reviews/MSI/R9_270X_Gaming/9.html