On average they should perform similarly. Note that the 6950 can have it's BIOS flashed and turned into an HD 6970 using a simple procedure. There is a "hard" BIOS switch to provide an additional safeguard in the case that any issues occur. If you are interested in taking advantage of thie BIOS flash, go for the 6950. If you would prefer to stick with NVidia (nothing wrong with that) go for the 560ti. Either are good options that provide great value. Reviews of both cards are available on this website, Guru3d.com, anandtech.com, and many others!