This is a great question that can be answered 2 different ways. My first answer is that biomedical engineering is a sub-discipline of engineering; therefore, you would be better prepared for your master's program with a bachelor's degree in engineering (and biology minor). My second answer is that biology and engineering are inherently two vastly different fields; so which one is more interesting to you? If possible, an internship in both fields would give you some firsthand experience so that you might discover your interests and strengths fit one area over the other. Also, biomedical disciplines are primarily human-related, whereas biology pertains to all living things (including plants and non-human animals). This means that if you decide to pursue an engineering major and biology minor, make sure there are electives within biology that fit your biomedical interests. Best of luck, and enjoy your journey, as biomedical engineering is an incredibly exciting field!