I second sophielophie that you should get some work experience because you'll be able to see what actually goes on in each profession.
Content wise, the science you learn in both courses will overlap, but of course, there is focus on the teeth/jaw in dentistry. So I would say that a simple determining factor would be your interest in teeth/oral/maxillofacial surgery. It really comes down to personal preference, and if you can't see yourself working as a dentist, looking at people's mouths everyday, then you might want to rethink that. Some people know that they are interested in teeth from the start, so dentistry suits them. Medicine gives more room to explore, because you rotate between different specialties and find out which one you like during your training.
Satisfaction really comes from doing what you like, and finding meaning in what you do. I'd advise you to go for job-shadowing/placement/work experience first for both dentistry and medicine to see what they're like. Then have a think about which one you like, and find more meaningful to you.
From what you've written, seems like you're leaning more towards medicine at the moment but you're concerned about the downsides. And it is right to be concerned, because it is a big commitment. You will make a lot of sacrifices as a medical student, and a doctor. I'm pretty sure it holds true for dentistry as well. The question is whether you feel that the sacrifices you make are worth it. Whether you believe that running shifts on shifts are worth it for the sake of your patients. And your commitment to your beliefs will be tested again and again. It's not going to be fun all the time. But the thing is, if you truly love and find meaning in what you do, it will be okay. And you will find joy, and fun; the things you sacrifice will be worth it, and you will find a way to make everything work out in the end.