Open Question: I may want to become a Marine or an Army Officer after college…?

I’m currently a Junior at a 4-year University, and am majoring in Biology. My brother is enlisted in the Marines currently, he’s been in for about 1 year now. Basically I’ve always considered joining the military, but I decided to go to college and try to teach at a University level for biology related courses like Cell Bio. However I also want to join the military out of my own personal inclinations, and other things like getting help with my student loans and finding solid employment. What should I know? Obviously I will contact a recruiter’s office, but maybe tomorrow. My brother also mentioned the Army has a better/easier time becoming an Officer than the Marines. Blast me with info if you can, I want personal feedback, I can find FAQ’s and other stuff from the military websites and my relatives who were in the military.