BS or MS in Finance?

I'm considering going back to school, and I'm strongly favoring a career path in finance, maybe commercial banking, but mostly because I have more exposure to that. I'm a bank teller with a humanities degree (surprise) and I want a better track for advancement.

I've been leaning toward a B.S. in Finance with the intention of pursuing some of the internships and openings I see on various bank career websites but I'm starting to think that an M.S. might make more sense in terms of length of study and better opportunities. The downside would seem to be that an M.S. program would have a narrower focus and be more math-intensive.

I'd love some input as to whether it makes sense for someone without a real finance or mathematics background to pursue an M.S., and if general internship/job prospects would be that much better than with a B.S.