Kent,

I'm guessing you haven't received input to this question yet because it's a very personal decision.  First, Business Analysis degrees are relatively new.  What BA Masters program are you considering?  Also, keep in mind that it depends on where you work, what your particular company may value more, and the type of work you hope to do in the future.  

An MBA is almost certainly more widely understood and therefore provides more versatility if you find yourself unemployed and looking for work in the future.  But if you feel strongly about doing business analysis work then maybe ultimate versatility isn't what you are looking for.