ati hd 7750 vs ati hd 6770

Well HD 7750 if you have a weak PSU
HD 6770, need a power pin, And in a average both are more or less equall but the hd 6770 can overclock better

+1 to 7750.

6770 slightly edges out on performance.
But trading a slim gain in performance for much lesser power consumption is not the best of deals IMO.

So +1 to 7750.

i have corsair vs450 watt builder series smps then i should go for which card

7750 will be good for that PSU

BTW, please tell your full system configuration

intel core i3 540 3.07ghz
6gb ram 1333 mhz
intel dh55pj motherboard
corsair vs450 watt biulders series