Should I join the U.S Navy or Air National Guard?

I want to get Tuition Assistance to help me get to a Doctorate Degree. I also want to serve my nation as an Naval Officer or Air National Guard Officer and become a pilot. Which branch has the best tuition assistance and which branch gives you the best opportunities. I understand the National Guard is basically like reserves and don't get paid much, but which offers more during and later in the future?