I recently transferred AFROTC detachments from University of Maryland (crosstown) to Virginia Tech and I can honestly say that the detachments were basically the same. The only major difference was the size. A smaller school will let you get more one-on-one time with your officers, but you will have less people to compete against and be more likely to be ranked lower. At a larger school, it can be a bit harder to get to know your leadership personally and stand out since there are so many Cadets, but it also offers better leadership development opportunities since there are more people to lead. The structure, the leadership, and the Cadets will change so frequently that you will get a fairly consistent experience regardless of what University you attend.
Choose your school based on academics, location, and extracurricular opportunities. Does your son want to fly? Find a school with an airport nearby. Does your son want to be a Developmental Engineer? Find a school with lots of different engineering and development clubs. Find what will help your son's professional development and prepare them the most. Also, if your son wants to go to an academy, but also wants regular college life, maybe look into Senior Military Colleges—they're a lot more work, but definitely worth it.
As someone said before, proximity to a base and geographic location is more important than you may realize. At my old detachment (UMD), I was offered the opportunity to go to base visits and cool opportunities left and right. At VT, I have yet to hear of a single opportunity. Also, during things like Career day (where active duty officers come and talk about their career fields), you will have more people show up and will ultimately learn more. At UMD, we also had multiple people who were in town at the Pentagon come and speak to us, but that's unlikely to happen at VT since we're like 3-4 hours away from any major base.
It's a hard decision and will ultimately impact your trajectory for the future, but also know that you're always able to change that decision. Transferring has been one of the best decisions I made and it also gave me the opportunity to see two different operating cultures and helped my professional development a lot. If your son is ever considering changing schools, please don't be one of the parents that immediately shuts it down.
Also, as far as communication goes, don't let that first impression dictate your view of the school. The person who is manning the email may have just had an extra busy week or is on leave. One person doesn't make up the entire culture of the Detachment so give it a shot even if it takes sending a follow-up email.
Best of luck to you in your college selection process.