Depends where you go. BM or BMus tends to be more music concentrated. BA may feature more breadth in learning. BA may also signify less time to complete the degree than a BM.
Best thing to do is ask for a course plan for both degrees from the institution you are interested in. It will give you a much clearer picture.
Also think past the undergraduate degree. If you are planning on doing graduate studies you would want to do a degree that prepares you for it.
Topic: BA vs. BM in music.