If all you want to do is research then I would say a PhD alone would be more suitable. Why learn all that "patient care", do rotations, etc if you don't want to do that. Also you can get funding for tuition and a stipend if you do the PhD rather than going into Med-school debt (ok, so you *could* get that for *some* MD-PhD programs too - but they are really hard to get into and you are still doing all the rotations etc you have no real interest in) AND PhD programs are much easier to get into in general than med school. I personally can't imagine why someone interested purely in research would do med school...but thats just my take on it (btw I work in an academic research environment, so I don't think I'm talking completely out of my elbow)