Anecdotally, some years back I started developing pretty bad RSI from typing. I was also a pretty mediocre typist. So I switched to Dvorak and got serious about touch-typing. I found it much more comfortable and since then I've never had any problems with typing-induced RSI.
With QWERTY, I was doing all sorts of things to try to stop the RSI. I tried to control the position of my wrists, the angle of my hands, how I hit the keys. I experimented with wrist rests. Since I switched to Dvorak I found I didn't need to pay attention to any of that. I can type virtually continuously for hours at a time at >100wpm, and while my speed will drop from my hands and the muscles in my forearms getting tired, even at that point I don't get RSI.
I had another set of RSI not that long ago, but I determined that was due to using my pinky on the ctrl key in emacs. That's a pretty well known problem, but I had used emacs for quite a few years without it being an issue. At that time, though, I had started using org-mode in a big way and was using a lot of C- bindings, and hitting it that often turned out to be a problem after all. Swapping ctrl and caps lock (and using my ring finger for it) fixed it entirely.
Even if the studies say that the difference in speed is marginal, I'm convinced based on my subjective experience that Dvorak is much more comfortable. That's difficult to quantify, though, and conducting a high-quality study to conclusively demonstrate it is extraordinarily difficult.