MD-Phd (MSTP): What are the benefits?
Doing good translational research is hard because it requires a good understanding of clinical issues (both from the patient and carer sides) and a strong research background. In order to obtain those skills you need to spend time in the clinic and time in the lab. An MD-PhD program guarantees that you will have the opportunity to spend time in both environments. It is worth noting that having that opportunity doesn't mean you will capitalize on it. Further, you don't need to do an MD-PhD to have that opportunity.

Another advantage of some MD-PhD programs is that you can get funding for the MD side. If it is what you want to do, saving 100k USD isn't a bad thing. If it isn't what you want, trading a few years of an MD salary for 100k is a bad investment.