If your budget can handle it, I recommend the Hawk.
1GB framebuffer is sufficient unless you're playing a few games such as Metro at ludicrously high settings and it surpasses a 1GB framebuffer at 1080p with high AA/Anisotropic settings. I know a few other games do, some honestly, some people use absurd AA settings.
If you're going to do that it would be wise to get something with more power but not a full 2GB framebuffer since there are other Vram sizes you can get. But, in the 560 category your only option for anything past a 1GB framebuffer is the Palit card, which happens to be a full 2GB.
This was a big decision for me 2 months ago, I was debating which card to get out of the literal 2 cards you're also thinking about. I was thinking Skyrim would surpass a 1GB framebuffer so the Palit might be a better choice. After quite a bit of research and talking on the forums I came to the conclusion by the time a game I personally play would need more than a 1GB framebuffer the performance of my card would be insufficient, but, this is only talking about huge leaps in requirements, as even going a few mb over your framebuffer significantly decreases performance.
I still personally recommend a high end 560 Ti, as some offer almost 570 performance, like the Hawk.
Keep in mind, this is all relative to what you plan on doing, you might in fact need a 2GB framebuffer, or something higher than 1GB. You have to analyze what you plan on doing
.Edited by Ascii Aficionado - 6/7/11 at 1:05pm