its a fairly significant difference if you intend to run games like bf4 at maximum settings. the 760 is fine for medium or possibly high while the 770 can handle ultra. at 1080p of course. if running above 1080p your figures will be different.
in general thats the breaking point between mid level graphics (760) and high level graphics (770) settings being playable.
as for what is best for you... thats your own decision.
did you want to save some money and are willing to accept playing on lower graphics settings? if yes then the 760 works. did you want to play at higher settings and play games further into the future on higher settings? then get the 770.