My 0.019998765 cents, since we are AFROTC. It really does depend on how far that school is from his university. Will your DS have a car? How much support does the school give regarding the x-town ROTC program? Is he going to be in a specialty (i.e. scholars, honors) program? How will this affect his ability to juggle both?
If you are speaking about something like Columbia, Georgetown than it is doable. If you are speaking about traveling 30 miles by car, than I would re-think it.
For ROTC, they may not get that same intense leadership courses like the SA's, however, they learn the political game. I am sure it is bad form to say that it exists, but it does in the "real" military. If there are 2 candidates with identical records, including gpa, pfa, etc., and can only give 1 name for a particular slot, the one that has been there on GMAC nights, or socializes with the cadet commander will be the one they choose (unless a jerk), because they know that cadet, the x-town comes in for labs and pt and leaves.
People believe that ROTC is just about the 1 or 2 days a week, but it isn't. They bond and socialize together. Typically in their freshman yr, they are left out in the cold, since many will drop between fresh and soph. However, come soph yr, you are in for the long haul. The relationships change.
Let me give you our son as an example. He elected ROTC full ride because of the scholars program at his college. In the beginning of his fresh yr, he hung with his buds in his scholars dorm, as the yr progressed he started spending more time with ROTC. This yr, he is "rushing" not a greek frat, but a military frat. He is seeing life differently now. He knows this summer he will be TDY at camp eating bugs while they are partying. He is concerned about his gpa because it will affect his life after graduation. His roommates don't get why he is pinging over the shine on his shoes or they laugh at him while he pulls out the ruler for measuring where his name tag should be.. In other words, his life is changing and ROTC is a big part of that. He is fortunate his det is on campus. If he has time off between classes, but not enough to go back to the apt, he hangs in the lounge.
It is not only about the distance, but how he will be able to convert from a "civilian" world to the military. A long commute may cause him to miss out on that bonding. DS has good friends at ROTC, but they all are experiencing ROTC and college together. If your child goes to another campus, they may miss out on that.
May I ask why he is going to do X town instead of the actual? Is it that the college is smaller? Lower quality? Higher quality? Offers other ROTC, but not AROTC? What is the difference between the 2 that stops you from applying to the college with ROTC det?
Also TPG is correct, you need to spend a few hours there. Make an appt to meet the commander, and ask him to allow your child to speak to the cadet commander in ROTC. He needs to feel that he fits in that organization. They will sell the det, but you should be able to see the forest for the trees. Also, google the det for x town, and then google the dets on campus. Their web page will be a big hint on the size and their direction. Look at the size of the military personnel. Your child may have to travel 30 miles to be in a det with a Commander that is a full bird or stay on campus with a commander that is a major. You want them to be in an organization that has more experienced leaders. Most ROTC commanders take this position as one to position themselves out of the military (aka grey beards)