The best way to choose is to spend as much time as you can learning about each profession. Many dentists would be delighted to have you shadow them in their office. Spend as much time as you can in a variety of dental offices and try to imagine yourself doing these same things. I don't know for sure, but I would imagine that physicians would be willing to help out in the same way. Spend lots of time asking questions about what each profession is like. After doing this, it should be a lot easier to make the choice.