I was pre-med for a looooong time, so I can understand your interest in it. I think you'll find that if you go the vet school route, you'll actually learn a decent amount about the way humans work too, which they do for a couple reasons:
-researchers these days almost always have to try to apply for outside grants, and in biomedical research, with the current funding situation, this means applying what you're doing to human medicine. So you'll need to know how to apply human stuff to an animal model.
-some things are just not that well characterized in veterinary medicine yet that are better characterized in people (or vice versa).
-many people learn well (myself included) by comparative anatomy and physiology, applying what you know about yourself to something not as familiar.
So that being said, there's a couple things you can do with both humans and animals in the medical field, be it human or veterinary. You can go into public health, especially zoonotic disease (which there is a great demand for), you could do research in the human/animal bond (like therapy dog work), or you could go into biomedical research and apply animal models to people (or vice versa). A lot of research seems to start in animals in biomedical research, then goes to people medicine, then comes back to the animals in veterinary medicine. Hope that helps.