Hard choice, the i5 760 will be fast3er in games, both will rock though, i prefer the AMD platform and skt 1156 is dead in water with sandybridge, although not 100% sure about AM3 compatability with bulldozer, both rock though and will me more than capable..
Either of them will be adequate for your requirements.. The LGA 1156 platform though, with its support for both SLI and Crossfire, is a more feature rich platform to choose.. Couple that with the fact that the i5 760 is architecturely faster and superior to the X4 965, your choice becomes easier.. However, if budget is an issue and going for the i5 760 means you've to compromise on the graphic card, then i'd say its not worth it.. Stick to the X4 then.. Video card is anyday a more critical gaming factor over the CPU..
For all practical purposes, the two can be equivalently OC'd for 24/7 use. They will retain their relative performance. At the end of the day, its the luck of the draw how far you can OC the chip you just bought.
Both are great, its really whether or not you want to use Dual Channel or Triple Channel really. Also the lga1156 socket is dead, and I don't see the AM3 going anywhere unless they revise the x6 cores.