Very good (and important!) question! I had secretly wanted to be a vet since I was six, but was pre-med all the way up to junior year of college when I switched to pre-law (and switched to pre-vet in grad school while realizing I wouldn't be happy for the rest of my life being an attorney). One of the deciding factors was not wanting to have to put up with all the crazy administrative stuff that physicians have to. I wanted to practice medicine and work with patients and colleagues, not be filling out paperwork juggling insurance crapola constantly. That's why there is a lot of resistance to managed care in veterinary medicine, despite the fact it will probably help more people pay for high dollar procedures. They don't want to lose that autonomy and the extra piles of paperwork. Not to mention the CYA (cover your @$$) defensive medicine (though we have have to worry about it too, just not *quite* to the same degree, but it's getting there).
And as much as I think the respect you get as a physician is pretty cool, I don't like how you are likewise expected to drive a 50K luxury SUV or sports car, have a million dollar house, send the kids to private school, etc. Not that all physicians are like this, but there are expectations for having a certain lifestyle that vets don't necessarily have.
For what it's worth, on both SDN and on VIN, I feel I've heard more physicians (including my aunt and great uncles, both MDs at universities) say they wish they would have done something else. That the money doesn't come for a long time (mid to late 30s). That they've spent 100K on childcare for their kids they never get to see. That what medicine is like now is not how it was 10, 20, 30 years ago. In vet med, it seems that conditions are actually somewhat improving for our patients, clients, and practicing good medicine in general. Pets live longer and are generally cared for better, people care more animal welfare in food animal than they used to, we have most of the same diagnostic toys, treatments, and surgeries that the MDs/DOs have. Now, our debt load as future vets has skyrocketed, which will need to be addressed somehow, but I feel that vet med in general is better than it was 10 to 20 years ago, but I've heard physicians say the opposite is true in human medicine, where it's a lot more cookbook, more CYA, much less patient/doctor interaction, less pay/reimbursement, Big Pharma and Big Insurance taking over, etc. *shrug*
Not that vets don't say that either, but it seems like life is a teeny tiny microscopic bit more flexible as a vet. It seems a little easier to be a part time and/or relief vet if you want to spend time with your family. And there are a TON of different jobs you can do besides just private practice. There is some flexibility in human medicine as well, of course, it just seems that specialty is the standard because of $$$. I'll always kind of wish what it would have been like to be an MD, but if it makes you feel better on the vet side of things, you can always get an MPH. We also have to learn a good bit about human medicine anyways for a number of reasons which I can go into if you like.
Anyways, try to imagine yourself 15-20 years down the road trying to see what you will enjoy more. And get a lot of opinions from both human and veterinary doctors and see what their dreams and regrets were. If you had the same kind of autonomy that a lot of private practice vets, that'd be a harder choice for me to make. That's why I came to the conclusion that I did that I would be better off in vet school than law school and med school.