Massive ATAR probably just a result of the popularity contest--no difference in terms of getting into med/dent etc. Also, bioengineering systems IS offered in science, not just biomed. Also note that the defence and disease major is just a cross between the pathology and immunology majors (exact same subjects).
Some differences:
Biomed has some more 'streamlined' or focused subjects. In first year, you do 1 semester of 'chemistry for biomedicine' over 2 semesters of chemistry in science. Also, the 2 bio subjects in biomed are more human-focused, whereas biology in science has some focus on plants and animals too. Also in biomed, you are required to do a stats, maths and physics subject (unless you're doing bioengineering systems) in first year.
Second year biomed requires the completion of 2 subjects (worth 4 subjects) that overall are equivalent to completing biochem, anatomy and physiology in terms of satisfying med prereqs. One can argue that these subjects provide a better foundation for medicine/dent. There are also some exclusive (and compulsory) 3rd year subjects for biomed, but I can't really give much comment.
Is Science more attractive? Apparently not, but don't let that influence your decision. In terms of majors and hence pathways available, biomed is but a subset of science. If you want more options, do science.