Overall top-end speed of each card at max OC's (you can still OC the card regardless of motherboard) you're probably looking at like +10-30% FPS difference (depending on the game in question, and how good of OC'ers you got) in favor of the 560.
At the lower end of what's likely to be the average difference, around 15%, you're talking about a difference you're unlikely to ever see w/the naked eye (going from 50fps to 57fps, for example), and one which is unlikely to be large enough to allow higher 'max playable settings' on the faster card.
At the other end of possible average differences, say around +25% (going from 60fps to 75fps) you get into the range where maybe the 460 can play Crysis at VH w/2xAA, and the 560 can do it at the same FPS, but w/4xAA (or maybe even 8xAA).
So there's a chance you'll get higher playable settings with the 560 in certain games, but again it depends on how good of OC'ers you got in each case, and on teh game itself.
TBH the cards are identical in so many ways that the difference between them is going to be a 'base difference' of around +10% for the extra shaders and better z-culling on the 560, + the difference in clocks you're able to achieve w/your particular samples.
So look at prices where you'd be buying it, and take those numbers into consideration.
Edited by brettjv - 4/8/11 at 10:38am