Oh great, another "which branch is best" thread. Hasta
Seriously, check them all out for your career field. All have their pros/cons. I'm currently having this conversation with my friend's nephew. In the end, it's up to you.
My disclaimer. I did four years Active Duty Marine Corps, and 12 years Air National Guard in the same career field. I've been full time for a little over two years now (technician status, not AGR). My living standards are better on the AF/Guard side (when I'm activated). I would still trust my active/reserve Marine counterparts over most of my AF/Guard counterparts.
I've had the priveledge of working with all the branches. ALL are honorable professions. If I had to do it over again, I'd be torn between the Marine Corps, and the Navy. I'm proud of being a Marine, but my six months aboard the USS Nassua were the best six month of my Marine Corps career.
Remember, with the AF, if the t.o. says "touch the electric fence", you will touch it, or be written up by Q.A. no matter how much it hurts.

aperwork Oh yeah, they love paperwork...
All the branches have good law enforcement. It's My understanding that the AF teaches the Marine PMO's...but I could be mistaken. SFS/PMO/MP/Master at arms...all good. It's just a matter of what you want to deal with.
Don't overlook the Coast Guard.
As a former Marine, I enjoyed hearing AF people whining how their AEF rotations went from three months to four. Tell that to the other branches, and AF SFS
Seriously, also check out the reserve(pick a branch), or the Army/Air Guard. Same opportunities, just one weekend a month, two weeks a year.
Good luck. BTW, contracts are for 8 years. The balance is served in the inactive ready reserve. And yes, you can be called up.