The way McCoy was written and played, he was very believable as a real, flawed human being. His imperfect practice of medicine got even more pronounced in the films. In THE WRATH OF KHAN, Chekov comes right out and says that Khan "put creatures in our ears" -- and McCoy blows it off without so much as a tricorder reading. BIG mistake. In ST6 he has a bad time treating the wounded Klingon.
So McCoy is the best in terms of being a realistic human with flaws and frailties, even as that might make him the last STAR TREK doctor in a starring role you would pick to treat your own injuries.
No, I'd like to amend that: Flox is last, coming in just barely before Doctor Zoidberg on FUTURAMA.
To get the best treatment, I'd go for some 24th century high-tech from the EMH.