Yeah, I mean being in the same state as the school. All the states I've looked at don't count going to school as being a resident. Even if you go to school for a year or more, if your primary reason for being in the state is for education, they don't consider you a resident.
Poor title choice on my part, I mean benefit as in better odds of being accepted.
I bet departments shoot for a certain number of in-state and out-of-state students. I doubt they take anyone without regard to location. If they accepted all or a lot of out-of-state students their costs would double or triple or they would have to shrink the size of the program to stay within their budget. Now the question is do they set the number of in-state and out-of-state students based on the demographics of the applicants? If they aim for 50% out-of-state and 50% in-state, but 75% of applicants are from out-of-state, then being in-state is an advantage.