I think it's silly to compare them, the gameplay is just so different in both.
That being said, I enjoyed both. Though, I only played BF3 for a few months when I was still living my roommates then. When he moved out he took BF3 with him, and since I haven't been motivated to buy it. Not because it's bad, just because of money problems. XD
Would I buy BF3 for myself? Maybe. But while we're on the topic, can anyone tell me if the DLC for BF3 is required to play online nowadays, or can I play the vanilla game only?