As you might see , the hd 7770 is superior for following reasons:
1.) Higher no. of shaders 640 >384
2.)Higher texture rates
Moreover you can play latest demanding games in hd 7770...than in gtx 650 as you will be forced to lower the settings of the game for sure...
So no need of further explanation bro.....Go and get the hd 7770 and enjoy gaming....Cheers.