No experience with the 560 series, but I have a 5850 and GTX460 (both running identical mainboards, RAM and i7-2600k) and the ATI box suffers wierd graphics artifacting and a raft of compatibility issues with older games. My NVidia will occasionally show a zbuffer glitch in a couple of older DX9 games but it is far more stable and maintains a much better minimum framerate. This is just my experience, so take it as such. I'm sure others with equally small sample sizes can point to the opposite happening. /shrug