There are pluses and minuses to joining the military.
Pluses:
you'll learn greater responsibility and self confidence
looks great on a resume
will train you in something that can be used in civilian life - in some/most cases its equivilent to a degree in that field
you get paid while you do it
you'll meet some friends you'll keep for life (maybe, i'm assuming)
Minuses:
you lose absolute control of your life for 4 (or is it 5?) years, and possibily after that since they can bring you back
its hard to maintain a relationship with another person while in the military. Say what you want, but I'm well aware of many people who cheat on their husbands/bf's while they're overseas. I wish the most painful death upon those people - but it doesn't change the fact that it happens
you have no control over what field they put you in - you may sign up for one thing, but they will put you where they want you and you have nothing to say about it
you, obviously, are risking your life should you go into the battlefield
to me, the minuses outweighed the pluses. to each their own - i know it has worked for a lot of peple - but it is by no way the generic 'best' option.
(it might be for him, thats for him to decide)