The idea of UW biostat being a more prestigious program than CMU is just wrong. First, UW is a biostat program, which may restrict you from faculty positions at some stat department. Second, CMU is just as well-recognized as UW, if not any better. I don't think the CMU name will eliminate the chances of getting faculty position at ANY university. It all comes down to research interest. I think given your interest, CMU seems a better fit. Plus, CMU is one of the strongest in machine learning/comp bio, which are related to your research interest, if you ever consider going into these areas.