I'm a civilian MD and want to serve. I've read here that army has bigger hospitals, more interesting cases, etc .... Navy you get the large bases to work on, can work with Marines which interests me.
But who gets less crap dumped on them between the two? Where are you less likely to get an overpromoted O5+ RN bossing you around on your clinical decision making and let you just do your damn job as a good military doctor? Who's happier?
(btw ruled out AF for me. Sounds like the most cush but also the least respect for docs.)
I think we're all going to biased towards our respective branches, myself included. Some of it is probably also specialty dependent; note, I'm an Anesthesiologist. With that disclaimer I'll put in my two cents.
I think the Navy folks are happier. We have big hospitals, as far as military hospitals go. Army medical corps is bigger, so probably more to go around. As a med student I spent time a month at Madigan. Based on my from the hip comparison between Madigan and San Diego I don't a big difference in scope of care and services offered.
One of the side effects of GMOs is that it keeps physicians in the service longer. I think with more time already invested retention is improved. People are that much closer to retirement than when they finish their commitment. The Navy has more GMOs than anybody. I think with longer time in service it helps keep physicians in leadership positions, minimizing the pain of the O-5's you speak of.
Another opinion, which is not as applicable now, is the expectations of those that went into the Navy. I signed the dotted line in 2000 (before the war). Even in peace time the Department of the Navy has ships and Marines; they are constantly cycling through deployments. Even when the wars wind down physicians will still be going out on ships with the Navy. I think coming in the with the expectation that operational medicine commitments will be a part of your career makes it easier to deal with some of the issues surrounding military medicine. The Army is more of an occupation force. Since we're currently occupying a few places the expectations have changed, but I predict at some point they will shift back.
Finally, the Marines. The best for last. I'm about two weeks from taking a trip to Afghanistan with the Marines. Five months ago I was a civilian fellow; this represents a bit of change for me. All of my colleagues have had great things to say about deploying with the Marines. A lot of folks in my department have had to deploy with the Army as Individual Augmentees. They all say they would have rather gone with the Marines if given a choice. I'll keep you posted on that one.
So, my $0.02. Navy docs are happier.