Which is best for me, Roth or 401k?

I'm having a hard time deciding what will be our best choice of account, so I figured I'd post my situation and take advice. My husband and I are both 22. He is active duty Navy, so we are eligible for the tsp 401k. The military does not match anything into it. We are in a low tax bracket right now because I am in school. However, when I finish school (about 8 years) we will jump to a much higher tax bracket. My husband plans on doing 20 years in the Navy (he has a little over 3 in right now). So with that information taken into account, what would be the best investment plan for us? Thanks for your help!