Comparing the fatory OC'd models ..... and why not as they come with better coolers at same price ..... we see that the 560 Ti slightly beat the 6950 in a single card configuration but has waaaay more overclocking headroom. When paired up in SLI / CF however, the 560 kicks butt (over 100 fps).
Factory OC'd 6950 Frozr OC gets 484 fps in Guru3D's game test suite and 759 fps in CF for $ 240.00 per card. That's $ 0.50 per frame / a single card and $ 0.63 per frame in CF.
Factory OC'd 560 Ti (900MHz) gets 495 fps in Guru3D's game test suite and 862 fps in SLI for $ 215.00 per card. That's $ 0.43 per frame / a single card and $ 0.50 per frame in SLI.
It all becomes moot however as in just 9 days we'll see the arrival of the 560-448 which is a hybrid 560/570 w/ 448 CUDA cores for the same price as the current 560.
http://www.tweaktown.com/news/21520/nvidia_s_geforce_gtx_560_ti_448_cores_packs_a_great_green_punch/index.html
http://www.guru3d.com/news/geforce-gtx-560-ti-448-core-gets-detailed-launches-nov-29/
The GTX 560 Ti 448 Cores will be officially launched on November 29 from what we heard, and its recommended price is expected to be on par with that of the original GTX 560 Ti.