They are close, I prefer the 660 (Nvidia) but other will like AMD cards better. The 660 will be better all around to a stock 7850, but the 7850 can over clock quite a bit. What games do you play?
Minecraft, sims, GTA, bf3, NFS. and more stuff. i heard the 660 bit is 198 or 192 bit only, while the 7850 is 256 bit.... what do you think?