Well, what branch does he want to serve in? That should eliminate 2 ROTC scholarships and 3 of the service academies right off the bat based on that answer.
After that, I’d look at what his top choice school is. Go to admitted students’ weekends and get a feel for how life is as a student at that school.
Does he want a more normal college experience? Or does he want to attend a service academy? Remember, everyone commissions as an O-1 and gets paid the same…
If leaning towards ROTC, which schools host the unit? Which schools are cross-town? For example, Princeton hosts Army on campus (it’s a fantastic program for sure), but Navy is at Rutgers. If you want to do NROTC at Princeton, just know you’ll have to commute some for NROTC activities.
Intended major could be something else to consider as well.
I’ve heard great things about NROTC at Duke, UCLA, UNC, UVA, and UT Austin. Princeton Army is amazing too.