Pros: They'll really fix you up and set you straight. Probably can't get any more hardcore than them. Lots of opportunities provided by the Marines.

Cons: They make you do pointless stuff sometimes. You'll get tired and stressed out quickly (especially if you're in a relationship).

Reference: My fiance (who's currently on deployment). 

Kind of late, but I was browsing the threads so that I can post a new one.