The answer to your question like any other on this site is "it depends"
Seriously though, what I mean by that is the basic questions of why?(do you want to join the military), what?(do you want to take away from the experience?) should come before the who?(should you join in the end...).
My little story:
I'm currently in the Army Reserves as a 2nd Lieutenant, Platoon Leader in my Military Police Company, I took my Oath of Office in October 2007. Previously I had enlisted into the Army Reserves after graduating college in 2003, I did it this way on purpose because at the time I believed I would be a more effectual officer had I served in the enlisted ranks for a while and making my decision from there.
I've always had a strong sense of patriotism even as a teenager but was convinced by my parents not to apply to West Point or the Annapolis for college. After 9/11 I had seriously contemplated dropping out of college to pursue the military but decided the military would be much better served with my graduating with my B.S. in Electrical Engineer than running off half cocked and deserting my education. I chose the Army because it seemed like the Navy and Air Force were giving me the run around when I started to inquire into things. I didn't really think about the Marines, no particular reason, just didn't.
At the time I just wanted to serve in the Reserves and didn't really go into the specialties as much as I should have. I chose military police because at the time it sounded exciting and it's wasn't want I did in everyday life as a civilian.
I perhaps should have chosen a branch of service that could have better utilized my Electrical Engineering degree, don't get me wrong I love the MP Corp. but I don't have much desire to go into law enforcement on the civilian side.
I do think I made the right choice in enlisting first and becoming an officer from there. My friend who is a naval aviator couldn't understand my reasoning, but we have different jobs and roles in regards to our subordinates. I may be responsible for the lives of people in my platoon out in a sandbox or on a mountain, they have placed their lives in my (and my platoon sergeants) hands they are my responsibility.
For active duty you can enter as an officer via OCS or ROTC as far as I know, if you enter via the Army National Guard/Reserves there is another way but I'm not sure if it is still an option.
The overall ASVAB score is not as important as the scores that come out of your ASVAB which are different for each service. More info here: