assuming you are buying it new, the 7770 is officially a better card than the 6850(at the same price) after 12.11 "Never settle" driver increased the performance of the Radeon 7k series in several titles. Its also lighter on the power supply compared to both cards.


comparing the 6850 to the 550ti, the 6850 is generally better, but can lose out to the 550ti on certain DX11 titles, as for some reason, the 68xx series doesn't handle DX11 as well as its future counterpart.