Really think about what you've been saying in your interviews and whether it is in-line with the philosophy of MD-PhD programs. Unless your GPA is just horrible (and even if it is) I would bet there are definitely other factors working against you. Again, if those are things you think you can improve, I think it would be worth reapplying. Just my opinion though. While the "job security" of an MD is an okay thing to have, if you see yourself in research in the future and with$200k in debt, that job security won't be to comfortable on the salary of a post doc. The truth is that if you're in that much debt, you will likely come to your senses that a career in research is not sensible and end up spending most or all of your time as a clinician. Sorry to put a lot of pressure on you here, but I think this is really a career decision that you're making at this point.
If you already know you're going to spend most of your career in clinic, then the MD-only option isn't looking so bad.
Agree with this. If you're not sure that you want to spend 3+ years in lab (and continuing on as a fellow, etc. down the line) working harder than in med school with an uncertain timetable for defending and hoping like crazy that your project does not get scooped tomorrow (!), I would take the MD acceptance, especially if the debt load is not going to be overwhelming.
I'm not bashing the MD/PhD path and I think it's the ideal way forward for certain people. But I think at application we gloss over what it's really like being a PhD student, which is a very, very different position than an undergrad researcher, with a lot more left up to chance and the quality of your mentorship. I would say that unless you love doing basic research so much that your career would not be complete without doing it in a substantial way, the better path forward would be MD only. Do NOT treat grad school as another chance to find out "if you like" the bench enough; you'll probably get burned and burned out. If, on the other hand, you do feel incomplete without being in the lab, you may do better to take a year out and reapply.
Two other things: there are opportunities for a well-funded year of lab research in medical school, usually between MS3 and MS4. Many students find these to be beneficial: it's a shorter time committment, thus you typically get a better project that's already cooking, better mentorship because your PI knows that you're not going to hang around for years and would hopefully try to help you get something done in a shorter amount of time. Many students going this route do publish. This also allows you to steer your science interest in the direction of your chosen clinical field (since many change their minds several times during med school).
I will also say that based on the experience of myself and others I know, a PhD can certainly help with getting into residency, but if you kick butt in med school and do well in the year of research, you'll probably get more interviews in most specialties, including the most competitive ones, than a MD-PhD (for reasons we can get into).
Best of luck, congrats on the acceptances, and feel free to PM.
