I feel you lockheed - I posted a similar question a little while back. I am entering a PhD program (biomed) and am second guessing (see name) my decision, wondering if I should try to get into my school's MD/PhD program (if possible - it's impossible to get in normally and I have yet to contact the program as I want to be 100% sure I want to open this giant can of worms...). I have found that there are very few of us (people on the PhD side of the MD/PhD - most 'lean' MD... as I was told during my PhD interviews when they asked me if I ever considered MD/PhD - some of my interviewers were MSTP program adcom members and they did seem very interested in the idea of encouraging more research focused students to do MSTP). PhD vs MSTP is never talked about - all I can find are articles, discussions, advice on choosing MD vs MSTP.