Picking a running mate from NJ would make sense because NJ has a large population. But I don't think Christie would take the job. I say this, because Christie said he would not. Rubio also said that he would not run for VP as well.
Perry would be ideal, because of being from Texas, but would be a bad choice in light of the fact that Perry is a demonstrable ignorant goober.
Biden was not chosen for regional reasons, that is pretty clear. He was chosen for his long experience in Congress, I think. Also, perhaps Obama and Biden hit it off well.