hey, I made a similar thread a bit earlier:
http://www.tomshardware.com/answers/id-1772101/760-windforce-770-windforce.html
Some very good responses from there.
"Well I shud first point out in both cases, the MSI is faster
http://www.techpowerup.com/reviews/MSI/GeForce_GTX_760_TF_Gaming/30.html
MSI GTX 760 Gaming 1180 MHz 1960 MHz 87.8 FPS
Gigabyte GTX 760 OC 1190 MHz 1850 MHz 86.6 FPS
http://www.techpowerup.com/reviews/MSI/GTX_770_TF_Gaming/29.html
MSI GTX 770 Gaming 1200 MHz 1985 MHz 101.7 FPS
http://www.techpowerup.com/reviews/Gigabyte/GeForce_GTX_770_WindForce_OC/30.html
Gigabyte GTX 770 1225 MHz 1960 MHz 96.0 FPS
The law of diminishing returns dictates that as performance increases, performance per dollar shrinks. The 770 is about 21% faster than the 760"
"You are doing the right thing, which is to check the cumulative score on TPU, but then also go to the individual benchmarks to see what that translates to terms of FPS on individual games. Definitely check out the games that you are likely to play to see. Obviously, 2-5 FPS is meaningless, but in other games the extra horsepower of the GTX 770 could make all the difference.
In terms of GPU architecture, the GTX 770 offers nothing special over the GTX 760 other than higher performance. They are both GK104 chips with a 256-bit memory bus and 2GB of VRAM.
The best philosophy, if the funds are available, is to go for the higher performing card that you can afford. That will help give you peace of mind and avoid "buyers regret" for getting a lower performing card. Even if it's not apparent right now, there might be a situation in the future when the extra horsepower will come in handy. For me, I can usually justify it by telling myself, it's only a couple more monthly credit card payments, or something like that. "
Hope that helps!