BF3 favors nvidia, while FC3 favors AMD a little. It depends on what you like. I've owned both Nvidia and AMD cards, not a fanboi of either. I like to buy one, then the other with each new system or upgrade. Drivers from AMD haven't given me any problems, BTW.
Personally, I'd get the best cooled card with the best warranty. ASUS, MSI, or any of the brands with at least two fans keeping the card as cool as possible under load is a priority.
The 660ti is worth $200 to me, but prices are much higher for both - get one on sale if you go that route. Find a deal on either.