Dartmouth MD you spend the whole 4 years in Hanover, Dartmouth-Brown you split 2 years in hanovoer and 2 years (clinical) in Providence RI.
Some people dont like the somewhat undiversified patient population of the Hanover area and so they choose the Brown-Dartmouth program because there is wider patient exposure in Providence. However, I'm not sure exactly how much better it is there, i will defer to Providence natives to tell you about that.
I chose the Dartmouth program because if I had chosen to go there, I'd like to stay with the same group of classmates for all 4 years. Plus, I think its slightly harder to get into the Brown-Dartmouth program because there are fewer slots available. Keep in mind that if you choose to do Brown-Dartmouth, that the vast majority of your classmates at Brown will be part of the combined undergrad-med program in liberal medical education. I dont know if thats bad or good, but just smething to remember.
Did you already go on your Dartmouth interview? I would get that program request sheet back to them pronto because they absolutely will NOT make any decision on your app until they know whether you prefer Dartmouth or the Brown-Dartmouth program. And if they accept you, they expect you to go to the program you indicated a preference for on your sheet. I dont think they will let you switch programs.
I honestly dont know much specifics about the Brown med school, so thats also partly why I chose Dartmouth. You have the option of interview with the Brown program while you are interviewing at Dartmouth, I'm not sure if the visit to Brown would be used to evaluate you or not though.