I'm a Navy man myself and the only really useful advice I have about making that decision is to explore all your options. There are peculiarities to each service that may be desireable or not. One of the things I've heard about the Air Force is that you may be required to do an overseas tour unaccompanied, which may be a problem if your married or in a serious relationship. It may have changed or only be applicable to enlisted personnel. Joining the military is a big decision and I know when I joined (both times) I didn't really think about the little things that may have swayed me from one service to another, or even away from the military at all.

Perhaps my father's advice might be better than my own: "Don't let your meat loaf."