I like Hypertrophy's strategy and I just might go that route. Hypertrophy, did you just ask for two letters from your recommenders, one for phd and one for md? Or you are just that great of a superstar that you have at least 6 people to write your recommendations?
Oh. Right. Um.... Actually, my strategy is truly awful, which anyone who gets to medapp secondary burnout could affirm. I don't recommend it unless you really have no other route to a decision. It's expensive (I happened to get some grad fee waivers because of my summer research programs so that helped) and time consuming and nerve fraying. My grades plummeted last semester because of my "strategy". The only way I could in good conscience tell someone else to do this is if you also follow this advice:
Apply to med schools really freeeking early and
finish your secondaries in the summer before classes start. (!!!!!)
Once that is out of the way, take the GRE (October), send in your scores, and do your grad apps. It's a very different mindset for everything from the statement of purpose to the kind of ECs you list, but it's a lot easier after however many medapps.
As for recommendations, I had one research professor overlap with my recommendations, and I did have him write two separate letters. I worry, though, about letting on to LOR writers about my indecision. All of my med recommenders (5) knew I had considered the PhD, but only one knew I was seriously going through with it. And for grad apps, two knew, one of whom wrote a second letter, and one had known in the past that I wanted to do MD-PhD but didn't ask about it when we met.
If that's confusing, here's the breakdown:
Med LORs:
Drs A, B, C, & D - knew I had considered grad, didn't know I applied.
Dr E (professor at a med school)
Grad LORs:
Dr E (professor in my putative research field)
Dr F - knew I also applied to med
Dr G - knew I had considered med, but didn't know I applied.
While I worried that this might be deceptive, I did have the option of keeping my possible futures totally separate but gave Drs E and F the chance to rock the boat, and I think it was important to not cloud my other (less familiar) recommenders' opinions with my own doubts.
Moral of the story: you don't have to tell everyone the whole story.