Not knowing your son, I would still say in most cases it is best if he goes to a sober living facility. Getting out of rehab is a fresh start, and I think a new location provides more of a fresh start. Moving home is like losing ground, in my opinion. Too many triggers, and way too much emotional toll on you. As a parent you can't help but take some emotional responsibility for his sobriety. Plus I believe they pick up on our anxiety about their recovery, and that doesn't help them in their recovery. Something as simple as a bad day becomes a much bigger issue than it needs to be. I also think that for his sake, he needs to do this on his own. If he is expected to earn his own way and you give him room and board, he really isn't functioning independently.
If he moves to a sober living facility, I guess my vote would be that he needs to go as far as he needs to get a fresh start. Being in your town means he will be exposed to the same triggers and circle of friends that he associates with using, and at 30 days he is very vulnerable to those influences.
My son has done rehab 3 times. The first two times he was in our city, and as soon as he got "travel" privileges he was at the door begging to move home. This time he is about an hour away. It's close enough to visit but far enough that he doesn't rely on us too much. Visiting with us is an "event," rather than a daily thing. And he's in new surroundings with new friends.
I don't know if that helps. Congratulations to your son on finishing his rehab; that's a real accomplishment!