Vantaggi
You get to serve your country which brings with it a sense of purpose that you cannot find anywhere in the private sector. I left immediately after my 4 years and the first thing that everybody misses is the profound sense of purpose. In the military, your objectives are usually very clear and you are devoting yourself to security of the country. You are contributing to something beyond a quarterly profit or anything a company could offer.
Svantaggi
Sometimes you will be over worked. It can be difficult to move around within the Navy after you've received your training. It will take time to change your rate. Also, while performance is important, what is most important is seniority. You could perform far better than your coworkers but simply because you've been in for a shorter period, you won't receive the best opportunity to advance.