Norwich University (an SMC) has all branches- Army, Air Force, Navy, Marine, even those pursuing a Coast Guard commission (although there's no ROTC for Coast Guard). Being a student from here, there is a lot of perspective gained in the Corps of Cadets from many students wanting career fields in these various military branches as well as students not wanting to go military and going straight into the civilian sector. I can confidently tell you that I could explain the different ROTC branches pretty well as far as training (Army advanced camp, Marine Corps OCS, Navy summer cruises, Air Force SFT), commissioning status (Army branching and components, Air Force rated vs non-rated officers, Navy Restricted Line vs Unrestricted Line, Marine Corps ground and air contracts). That's part of the beauty of going to an SMC like Norwich. You gain knowledge about different branches and different types of work people want to get into. I just learned this year that we have a couple of students contracted with the DOD and "commissioning" into the NSA for cyber security and mathematics. In result in knowing all of this information about different career fields, many students are able to switch to different branches or lifestyles and not "screw" themselves in going into something they don't want to go into, but are "obligated" too, because they don't know any of the other career fields otherwise.
As far as camaraderie between the ROTC branches here, we have an annual football game between Air Force, Army, and Navy (Marine Corps included in Navy). There are service protects that each branch assists each other in.
There is obviously some "poked" fun with each other, as Air Force Cadets call Marine midshipmen "crayon eaters", or the Marine midshipmen refer to the Air Force as "chair force."
This is just from my experience from this school I go too. Ultimately, your DS has to look into a school that he believes will be a right fit for him in knowing that is where he wants to be for the next 4 years.
I hope this helps.