HALO 4 VS Black Ops 2 : Choosing Between Similar Games?

I'm aware that COD and HALO 4 have never been very similar aside from being FPS based but with COD BO2 being more futuristic, I'm now a little compelled to pick that up. I haven't opened my copy of HALO 4 yet so I've been fighting with myself over what to do. Yes HALO had gotten glowing reviews but thats not to say COD won't do the same.

My budget simply can't stand getting both games in the same month, especially not with the Wii U on the way and thus the plot thickens.

Let me ask, which game are you picking up....why and what swayed you one way vs the other?