Heres what I know so far and you can tell me if I'm wrong or something.
Marines: They may not give you the whole load of chioces like the Army and Air Force but,like the Navy they do have lists of jobs that are available and like they said the more of these jobs you take the more you can excel and get promoted. Also the marines are
The biggest group of badasses since the Roman leigionares.
and are the number 1 fighting force in the world when it comes to aggresiveness.
Army: Alot of job selections and never goes out but, they can be sometimes lazy and also act like a police force instead of a actual fighting machine that puts fear into peoples eyes.
Air Force: The brains and the only ones that have an extremely high percentage that go to college and become the big guys in the military or could be the coms or watching the people on ground, sea, and air to make things safe and work properly.
Navy: #1 fleet in the world. Great minds. And could survive without any of the other branches (Air Force and Army). The Marines are funded by the Navy and don't like to admit there part of the navy. They also have the #1 academies and colleges around. But also like the marines have a selection of jobs that can be taken up that may leave you to a grunt, or a desk job answering funs, and checking paperwork.
There is more but thats what I'll leave it at.