Vantaggi
Job security is solid. It's also rewarding work that you can be proud of. There's a solid promotion system (mostly by how long you worked) and also huge array of recognition for performance (military awards). Pay is not spectacular, but it is not too bad with things like housing allowance. Great leader development. Even if you lack experience as a leader, they will definitely throw you into a position where you must develop as a full-fledged leader.
Svantaggi
It's not for everyone. Work is very dangerous. Expect working all day and every day when deployed. Also your leadership could be a hit or a miss. You have real gems amongst the leaders, but others may be Prima Donnas with no clue of what they are doing (thanks to job security they made it up the ranks on the virtue of being in the military for a long time).