All things being equal, it typically doesn't matter. It's about what he learns (and can articulate) regarding leadership from the program. The Navy and Air Force are very capable of teaching military aspects without CAP or Sea Cadets. For USNA, we look for applied leadership and that the candidate has learned from that leadership expierence. He can gain that from CAP, Sea Cadets, Boy Scouts and many other organizations. It's not about wearing stripes or obtaining a certain position ... it's about starting the leadership journey and learning from it. The interviews we conduct do not ask about military aspects...they do cover, among other things, "Responsibility" and "Leadership Potential". He should also have Plans B & C to become an officer.
Explorer programs that I know of are usually sponsored by a local Boy Scout council so its definitely a program that would add to his leadership resume.
During my CO tour my base hosted a sea cadet group. They'd get to do their weekend events on my base, interact with the sailors, etc. All else equal between the two groups, if one of them has a connection to a local military installation I'd go with that. But as others have said, both are great.
Good point, CDR.
Explorer programs are part of the Boy Scouts of American, so you can report Boy Scout participation. Explorer posts can cover a wide variety of career learning fields -- I actually ran a Legal Explorer program for a few years.
This one is actually run by the County Fire Department in my city. Sounds like a Boy's Scout thing but it is different...it is a firefighter prep paramilitary program...the police also have their Explorer program in my city. So the name is similar, but not a Boy's Scout program...more like a firefighter's JROTC program if I could compare it to something.
Unless I'm totally off base here, there are a number of types of "Explorer" youth organizations but all of them come under the Boy Scouts of America (Scouts BSA) organization umbrella.
Why not have your child attend both, to see which one is preferred. Most will allow you to attend as a shadow or for an 'open house', as my youngest went to both and shadowed. This can give you a better idea of what group might be a better fit. Our Sea Cadet program does have a wait list, and there are PT requirements to join. So if not ready with the mile run and PT, your child may want to start getting that underway.