I would like to say something here about MBA/MD and Wharton in particular.
As noted above, the MBA is certainly not a research degree. If you plan to contribute to the field of health policy, there is nothing better than a PhD in Economics. Wharton has a PhD in Health Care Management, but if I were you, I would do a PhD in Econ and specialize in health economics.
The MBA is nothing more than a rehash of an undergrad business major. It looks much better than it really is.
Now, about Wharton in particular. It's arguably the best business school in the world. I would even go so far as to say it has the best finance program, hands down. However, you won't find too many likeminded individuals interested in the health care field. At Wharton less than 1% of the students choose a health care management concentration (I would say most of those wind up doing a second concentration in finance and work as analysts on wall street specializing in the health care industry) Everyone is geared towards finance and landing that IB, hedge fund, or VC job. You will be lucky if you find any other students seriously interested in health care policy. It's a shame really, because you see amazing students with great experience and qualifications selling out just to wind up as first year associates on Wall Street.
A huge bonus of Wharton is the name. While I don't think it will open as many doors for you when it comes to applying for residency as spending that year doing pure research, it will open many doors for you socially. Also, if you ever decide not to enter residency after medical school, even without work experience, you may be able to pull off an associate position instead of an analyst position.
I still believed that I was the victim of deception when I observed the phenomenon of the ray.