It might be hard to convince schools that you're interested in the health and wellness of your fellow human being after spending six years learning new and interesting ways to kill them.
What an idiotic comment.
I've known several people who have gone from SF into med school at places like Tulane, etc. ADCOMs generally find those sort of applicants a little more interesting than the "I've wanted to be a doctor since I was three" crowd, and they generally have no trouble getting into places.
To the OP: If you want to do it, you can. I was an Infantry Officer who completed Ranger School and spent a year in combat and, though I wouldn't want to do it again, I am glad for the experiences I had in the military. I've had multiple interviews and acceptances and have never once been asked a stupid question like "why do you want to be a doctor after learning new and unique ways to kill people?". If I do per chance get it in any of my next three interviews, I will most likely look at the questioner as if they had a stump growing out of their head.
The only advice I give to people who are thinking about serving is to do it for the right reasons. Money is not a good reason to serve in the military.
If you are dead set on doing it and are ambivalent towards the different options you have, join ROTC, try to commision as an Infantry Officer, and then fight for a slot in the 75th Ranger Regiment. That way you will only have a four year active duty obligation (make sure you research the IRR too, all military obligations are for
eight years, not four) and then transition to Med School.
If you do SF, SEALs, Delta, or whatever, you are going to incur more time. By the time you get done with all of that, you will be pushing thirty when you start Med school. Furthermore, as you move up the elite ladder the selection process becomes ridiculously hard and you stand the chance of not making it and spending you time in the military doing something you don't want to do.
BTW, the Army recruiter might tell you that you can go to a SF team as a Doc, but I wouldn't believe anything they tell you. Those slots are generally filled by doctors who were SF qualified before they went to medical school. There are plenty of them (reference my first paragraph).