I was talking to a post-doc interviewing for a tenured tracked assistant professor position in our department. He made a comment that candidates who have a MD have an easier time landing their first assistant professor position. I replied that it was probably because many MD/PhDs were taking positions as instructors or non-tenured tracked assistant professors in clinical departments and get no start-up funds. In contrast, that candidate was interviewing for a tenure-tracked position and asking for a one million dollar start up fund. The bar for hiring a MD/PhD to fill a non-tenured tracked assistant professor/instructor without any start up fund and with no pay for time spent doing basic science research is probably a lot lower than a PhD looking for a tenured track position with startup funds right?
Sort of. You are sort of right because the scenerios you present are essentially true- those who fill instructorships or non-tenure tracks will of course have an easier time getting an academic position, albeit a temporary one. For those interested in research, these typically only last 1 year and act as a bridge to your asst. Prof. position (they give you an additional year to come up with data before the clock starts ticking). There are no guarantees from the department that they will hire or promote you, but if you look good you have a great shot. Of course, this isn't an assist. prof. position (or pay) so you didn't directly address the post-doc's comment. Also, non-tenure asst. Prof positions are also easier to get, but they are typically reserved for those who will not be doing any significant research (i.e., clinical track). So again, you are outside the intended scope of the comment.
I actually agree with the post doc. It IS easier to get an Asst. Prof. position with the MD. It is all about finances for the department. As an MD you provide significantly less risk to the treasury than the PhD-only counterpart because as an MD you can provide billable services to the department that will help defray the cost of your research. For example, if you do an 80/20, that means 20% of the time you are providing revenue for the department that is guaranteed, compared to 0% for the PhD-only. If you are a PhD-only and secure $1M and after 5 years fail to get an RO1, then you just cost the department a lot of $$ and they will show you the door. If you have an MD, they will just raise the amount of time you will be doing clinical work to compensate for the lost investment, so you still have a chance, a lab, and a job. A lot of this is dependant on the department you are in, of course. In medicine, your billable time may not compensate the department much, so the playing field is probably more level. In any field that performs procedures or pathology, even a little clinical service can produce a lot of revenue.
Another issue is time- MD/PhDs can also get profesorships much more quickly (like right out of residency/fellowship). That's because you may have significant research time built in to residency and have grants lined up before even looking for a job. Bottom line is that if you want to have an asst. prof. job, you need to minimize risk to be an attractive candidate. If you have an MD, you've already reduced it a tremendous amount, but if you have an R01 you have a free ticket to anywhere. As a post-doc the same is true- if you can get an R01 or nice chunk of $$, you just bought yourself a free ticket.
Now if the comparison is between basic science and clinical professorships, then the post-doc is absolutely right. There is a demand for clinical service far beyond basic science research. It's not even close. If you want a job as a basic science prof at a top university, you better be awesome. If you want a clinical job, then you just have to be competent a lot of the time.