GTX 770 2Gb or GTX 680 4GB

Proofy

Admirable
770 is just a tiny bit faster than GTX 680

http://www.hwcompare.com/14636/geforce-gtx-680-vs-geforce-gtx-770/

but since you get GTX 680 4GB vram I'd take 680 instead, games today like GTA V demand more than 2 gb vram hence why I'd go for GTX 680 instead!
 
Lol the 680 and 770 are the same card. The 770 is a rebranded 680 thats just clocked higher. The 6804gb if a good asking price would be the better choice probably. You can always overclock it. Honestly though dont buy either. A 960 or 970 would be a better buy for the same price or maybe a little extra. A 960 can be had for under $200