Hi there,
I am going to disagree about "thinking" in medical school. Medical school is all about problem solving and those who do well, are the people who learn those volumes of materal and learn to apply it quickly to clinical situations. Medical school is all about clinical problem solving. If you are only a "regurgitator", you are going to have huge problems down the road. It's just not that easy.
I went into medical school with a Ph.D which served me well and continues to serve me well. I did research while in medical school and I continue to pursue research as a resident physician. I do not believe for one second, that you have to be passionate about reseach to obtain some benefit from the process. I totally believe that my research was one of the things that honed my approach to medicine and medical problem solving.
There are many roads to medical school and medicine. Doing a masters or Ph.D is one route and there are others. The best thing for me was that I didn't have to pay for any of my graduate coursework as I was on a department research stipend. This might have loads of appeal for someone who wants to do research, take additional classes and not have to pay for them.
Most of the competitive residency programs tend to favor people who have done research and have papers. This was already in place for me even though I continued to do research as a medical student. Am I advocating getting a Ph.D if you really don't like being in the research lab? No, but I do believe that there is value in doing research at any level undergraduate, graduate and while in medical school. Most of the program directors that I encountered on residency interviews tended to agree with me.
If I had not been accepted into medical school, I had already prepared my lectures for the next spring and fall. It kept me away from the mailbox as I waited for my acceptances. Another benefit is that you have something to do during your glide year, finish your thesis/dissertation.
Take the path into medicine that you believe is best for you but don't discount the value of scientific and scholarly investigation. It works on many levels.
njbmd