I don't really think a specific knowledge of any one subject makes that big a difference in the overall scheme of things. All it really means is that a few aspects of the program might be a little easier to grasp or require a little less work than others.
I think having a broad base is more important than any one class - you will forget the details of anatomy, pharm or biochem by the time you get to med school, but if you have a broad base in the sciences, you will have a conceptual framework to build upon and integrate new material into. From this perspective, things like cell bio, basic physics, genetics, chemistry become real important - if you have the concepts integral to these subjects down, you will find that these basic ideas are repeated over and over as you go through med school. If you don't understand the basics, you will be doing even more memorization to try to cover your lack of understanding.
That said, I would actually recommend an embryology course. At least in my experience, many students have a tough time picking up embryo during med school, and it really helps with a lot of anatomy and even some path. The concepts are foreign enough that being exposed to them at least once before med school would likely be helpful.