I was pre-med and switched over to pre-dent. And no I've never taken the MCAT, so I can't say I would have gotten into med school or not....
For me personally, after volunteering at a local hospital for about 1.5 years now, I realized that doctors (at least from what I was observing) don't spend any time with their patients. I mean in the rare even that a doctor walks into his patients room, he spends less than 2-3 minutes talking to them and moves on with his day.... now I am not saying he isn't doing his job, it just seemed to me that being a doctor in a hospital is not as human-to-human interactive as I thought it was.
I am a non-traditional student whos main reason for switching away from software engineering was that I wanted to work in an environment that let me use science & problem solving along with being interactive with other human beings.... Dentistry is perfect for this reason.
Now there are other reasons you hear about, like doctors working mad hours and dentists not working as much and how doctors are on call alot blah blah blah.... I mean I am sure its true to some extend but I can't exactly agree or disagree with it since I have never worked as a doctor or a dentist, how can I really be sure how their life/work style matches up...... For me personally, I know how I am, I am kind of a workaholic, if I come a doctor or a dentist, you can bet I'll be pushing 50-60 hours every week AT LEAST for the first 10 years.