To be honest I have a 560 Ti, and I love it. The new Fermi architecture is great for power as well as speed. It has plenty of cores, and you will be able to use the DX11 features. Plus, the card has gotten relatively inexpensive.
The card is also able to be dropped into SLI if in the future you don't feel it's enough.
That said, if you can currently run Crysis 2 with no problem than you will be able to play BF3 at maxed, or at least high settings without a problem too.
So, in the end, your choice. I personally recomend the 560.