Just spent a couple of hours swimming through old threads a few of which compared these in utility. In case it is not commonly known, aside from any difference in utility, I would like to point out the apparent difference in time required to obtain the ThD vs the PhD. Here I limit my observation to the typical US school: The PhD has as minimal entry requirement a one or two year MA. Then two years coursework plus dissertation. The ThD has usually the entry requirement of the ThM. The ThM is a four year masters with two languages and thesis. Then the dissertation. The differerence is two to three years more work with the ThD. Doesn't seem fair, does it? Oh well, I love my studies, so, more IS better!