Hi! I had pre-med friends from Sargent and CAS (more from Sargent though) and it really does come to where your interests lie.
Being a human physiology major is as close to being a pre-med major as one can get because most of the required classes for the degree are pre-med requisites mixed in with some anatomy, nutrition, and other electives. Plus you're required to do an internship which can help you get needed clinical exposure for med school applications.
BUT be warned that the anatomy classes are not easy! every human physiology major I know said that the classes are very extensive as if you are an MS-1 🙁
All of the other Sargent classes are very chill and virtually all the teachers are super friendly and helpful which is good for LOR.
Also, it puts pressure on you to do well overall in your major because if you leave with BU a low GPA as a human physiology major, you're pretty much screwed when applying to med school.
But if you have a good GPA, it can definitely help you.
For biology, the classes vary in terms of difficulty and scope especially since you can specialize as a biology major. So I know a lot of bio majors with good GPAs but also low ones. But being a bio major tends to make it easier for people to get bench research opportunities so that's something to consider.
Overall, though, it doesn't really matter what your major is for med school so long as you have the solid work ethic needed to do well in your classes.
I majored in philosophy which is different from all my other friends but I liked my classes and profs a lot and did well in them so it worked out
Hope this was helpful!