Not everybody wants to go to an osteopathic school. There are different reasons to choose between MD and DO. When I was applying to school I only applied DO. I wanted the extra training in OMT and love the whole person approach that osteopathic physicians use.
Some of my friends didn't want to go DO because they wouldn't be an MD. I found that interesting. Where I come from there are very few DOs and I spent a fair amount of time explaining what it meant, and answering funny questions like, "so can you prescribe medications or do surgery?" Obviously, the answer was yes. I really just want to be able to provide the best care possible for the patients that I work with, and to me that means the osteopathic approach to medicine.
Not all people want the approach that a DO uses. Often patients just expect to come in and talk to the doctor and walk out with a prescription. This works for lots of people… not me. A DO receives the same science background that an MD gets, but also gets 200 hours in osteopathic manipulation and more.
What I'd recommend is researching both MD and DO and then make a dicision for yourself. For me osteopathic was the way to go. For you it may be different.