A lot of medicine pathways or medicine alternatives e.g. biomed, dentistry, health science courses require biology as a prerequisite, so biology would probably be the better option. As stated above by GreenAcorn, some of the concepts in biology will pop up again in med as well (at least loosely).
For other subjects, either or both of chem and physics are generally required for med as well, and English subject i.e. mainstream, lit or Eng Lang (or EAL if you’re eligible) is a must for VCE completion. I’d also recommend methods for the most pathways towards med, even though med itself doesn’t require it.