My PhD was in molecular biology and in a field completely unrelated to ENT.
When I interview several years ago, no one really cared what it was in, nor really much else about it.
In fact, many programs were trying to push me towards the 7 year tracts in order to do more OTO specific research - which I was not interested in at the time.
If you want to go into ENT, my personal opinion is that the combined degree neither helps, nor hurts. It adds 3-5 years more to your training. Your research interests will likely change in residency, and it is exremely hard to continue productive basic science research when in residency - especially if you become married with children.
Personally, I wouldn't do a combined degree again, if given the choice. But that's me - and everyone is different. As a soon to be PGY-4, it would be nice to be several years ahead in training and done with residency at this point.
You can always do research in residency or opt for a K-08, K-23 or R-03 as junior faculty to get the bench research required to be active and productive - plus with these routes, the $$$ is substantially more than as a MD/PhD student (plus there is loan payback programs) and your research interests will be more in-line with clinical interests - as a student I would venture that you aren't really in a position yet to even know what possibilities even exist clinically.
Moreover, it is extremely difficult to be active at the bench and be a surgeon. To build a lab - you'd be looking at 2-3 days a week in the lab, 1-2 days of clinic and maybe a day of operating a week - hard to build a practice with such little time in the clinic. Funding for research is not what it used to be - thanks to the current administration. Current R-01 acceptance rates are ~11% - and you are competing against people with PhD's and 1+ post-docs and who spend all of their time in the lab - it has been demonstrated in multiple studies that the MD/PhD does not give the grant applicant any advantage over an MD or a PhD as their sole degree.
If financing medical school is a worry - don't let it be. Student loan payback will not be an issue once you are done -
Regardless, best of luck.
Leforte
PS - one more thing - your interest in ENT may change once you get to clinicals. I know of dozens of people both at my medical school and students who have rotated with us throughout residency that were seriously interested in ENT, then realized that "Yes, cool surgeries, but ENT doesn't stand for Easy Nights and Tennis and that I'll be living the life of a SURGEON - I think I'll do Anesthesia/Radiology/pick your favorite lifestyle, big money specialty."