I live in NC and he will almost certainly go to Uni here.
The state they plan to go to University is only important if you are looking at a plan that allows you to buy semesters of school by paying in advance. In these types of plans the returns you are getting depend on in-state/out-of-state and public-vs-private.
In a plan that works more like an Roth IRA where you put money in post-tax and as long as you use the money for allowed educational expenses the returns are not taxed, the main reason you pick your state is if you can get a state income tax deduction. If your state doesn't offer a deduction, then you should look at all the 529 plans and pick the one that works the best for you.
Since North Carolina doesn't offer a tax deduction, you should look at other plans. Picking a plan from another state won't gain you a state tax deduction, but in your case it won't cost you one either.
You can find many sites on line that will help you decide which plan to pick.