What branch of military should i enter?

I am a senior in high school and want to join a branch of the military after graduation. I want to become an interpreter/translator or something in the medical field. I have good grades, am a very hard worker, and love a good challenge. Which branch of the military should i enter? I was thinking along the lines of USMC or the Army. Which has more opportunities to offer me and do they cover the expense of my schooling? Thank you.