Military is good. Though make the best use of your time. Alot of people join, and end up drinking alot, going out. If you really are interested in making career advancement. Volunteer for every school you can get. Alot of units base who they send to schools on their PT tests. So train for the Marine Physical Fitness test. Take as many military schools as you can, and try to get in as many correspondence courses as you can stomach. They offer those in about every subject you can think of. ALSO... alot of units will give you time off to go to college, but you will still get your military pay. Take your college classes when you can, and work on getting your degree as quickly as possible, even if you have to take classes after your regular marine duty hours. Also... if your in the security field, go by the local police... alot of departmens offer courses for their officers, and will let active military in for free. IE... Baton, Mace, Firearms, etc. Now your probably wondering why do that... wont the marines teach me to shoot. Yes, BUT military education/training doesnt always transfer over to civillian life. So think about what your going to do after the military. Just my thoughts, hope it helps. Good luck.
PS... Army Rangers are the baddest SOBs on the planet.