Which graphics card should I get?

I want something strong enough to run BF3 and ARMA 3 relativity well. I don't need super HD for them just smooth gameplay without lowering my res too much. I've narrowed it down to either the NVIDIA GeForce GTX 560 Ti or the VisionTek - Radeon HD 6950. If you have any other suggestions please say and I'll give them a look too. Thanks