Your brother should make his decision based off what his desires are. There is a lot of "good advice" here, that is actually shit advice if it isn't what he is looking to get out of his service.
There are pretty much 3 factors he should be considering, Branch (USMC, USA, USAF, USN, USCG), Component (Active, Reserve, or Guard), and MOS or job.
A realistic evaluation of his position and what he wants out of it should be the primary guiding factor here. If his concern is getting his education covered, there are 3 good paths to this. 1. The national guard in the state he wants to go to school in. If he joins the MA guard, he goes to UMass for free. UMass is a great school. 2, he could do ROTC with a full scholarship, but those are not a given, and are competitive. 3rd, he does 4 years active duty and he has the post 9/11 GI bill. The downside here is this, if he wants to be in the USMCR or Navy Reserve, he'll have virtually no meaningful college benefits until AFTER he deploys, and right now those are far from guaranteed.
If he just wants an adventure for at least the next few years, I think he will get the most satisfaction out of doing an active duty stint. I was lucky in that I joined the USMCR and got deployed 2 years after joining my unit. I got my "adventure," and college benefits when I came home. I did 7 "satisfactory" years towards a retirement over about 6.5 actual years in the reserves when I got out. It's been a couple years, I miss it, and I'm now working on joining the army guard.
If he wants an adventure, granted I'm biased, I would say go Marine Corps or Navy. Both branches have incredible bases and incredible travel opportunities (depending on the job). The army has some bases in nice locations, but most are in crappy locations. The air force has nice quality bases, but also largely in shitty places.
Having not stepped foot into the army yet, but being decently well acquainted with it, and as a former Marine, I can say the Marine Corps is absolutely the most cultish fraternal branch. It's small, the traditions die hard, and there is a degree of self selection among members. This is not to say the USMC is better than other branches, though I do think they do some things better than other branches, but nobody will dispute its a cult. Now on the USMC front, I'd only go that route for combat arms jobs. The farther you get from the infantry int he Marine Corps, the more "stupidity" you see as far as the idiosyncracies of a garrison military environment are concerned. For a technical job or skillset, I'd stick with the Navy (for travel and location), or air force (for comfort and family-friendliness). Army and Marine Corps all the way for combat arms stuff, and Army is the only branch that has a pathway for a highschool grad to be a pilot, if that's what he wants.
On the VA/veterans treatment front, a VA hospital is not a petting zoo, and I wouldn't take him by there to give him a realistic outlook on what veterans face. Some veterans are ****ed up from their service, most are just fine. Here's what I face as a veteran, preference in a ton of jobs and grad school applications, outstanding leadership experience, and a virtually free ride through graduate school. The VA healthcare system in MA is excellent. I have nothing but good things to say about the hospital in JP. The ADMINISTRATIVE leg of the VA is a shit-show, but I've had doctors give me their direct emails, nurses give me contact info of nurses in departments I needed to schedule stuff with, etc. That said, the VA healthcare network varies a lot hospital to hospital. I had friends out in AZ, and it was every bit as bad as it is rumored to be. The lifelong and financial benefits from service are unmatched in my opinion, even with the "bad."
Mike
