Very happy with my 260 here - you're gonna get better quality AA with the Nvidia, the ATI can only run a full blown supersampling mode vs. the Nvidia combined mode and it's probably going to negatively affect performance on a 5770 (it's probably ok on a 5850 or 5870 though). You can run normal multisample AA with it, but you'll have shimmering because MSAA doesn't do anything to alpha-test textures/objects.

And to contrast, I'm happy with the 5770 performance here. Can't really compare the two, but the 5770 is ~$50 cheaper and it overclocks failry easily via the ATI drivers +160 mhz GPU, +200 mhz RAM. No added voltage.Super sampling seems to slow it down, but tbh, I can't tell the difference between 4x anti-aliasing and anything else with a 27" 1080p screen.