Is there a difference in FPS?

Solution
Not likely. You can OC your GPU yourself. And, changing clock rates by 20 MHz shouldn't heat your card too much. It's too small a change.
The OC edition will be ever so slightly faster out of the box (due to the clock difference you've already spotted), but both will likely hit the same clocks. The biggest difference appears to be the type and number of connectors on them.
 


No, not really. You can just overclock it yourself if wanted. But the the most expensive ofc has the best cooler. I'd get a GTX 650 ti for that Money, it's faster than the Radeon 7770.
 
The GTX650Ti is about $10 more, and it's also a cripple. It doesn't matter in today's games, but if some future game benefits from GPGPU processing (e.g. a good AI), the GTX650Ti will fall flat on its face.
Cleeve DOES pick it in his best gaming card for the money article, but it's in a higher price tier than the also-selected HD7770; then there's the cripple issue.
 


There is no such thing as, "future proof". It's about right now, and right now it seems as if GTX 650 ti is the best choice.

GTX 650 ti beats Radeon 7770. http://uk.hardware.info/reviews/3233/19/nvidia-geforce-gtx-650-ti-review-gigabyte-vs-msi-vs-zotac-geforce-gtx-650-ti-vs-radeon-hd-7770