I learned both Dvorak and Colemak, and ended up sticking with the latter.
I'd been a software engineer for 15 years, but I never learned to properly touch-type. My new year's resolution for 2013 was to learn to touch-type. In Dvorak.
I spent a couple weeks learning Dvorak at home, got up to almost 30 wpm, but it just didn't feel right. I went looking for something better, and discovered the rabbit hole of alternate layouts. I immediately dismissed Colemak, as it didn't seem to be "logical" like Dvorak. I spent a little time with Workman. I even designed my own layout and used it for a few days. Finally, I came back to Colemak and gave it a try... and it clicked instantly. Within 3 weeks I was using Colemak full-time, and within 4 weeks I was faster than I'd been on qwerty. I haven't looked back.
Dvorak and Colemak are both really good. Rather than worry about one being "better" than the other, I would recommend any potential switcher to try them both and see what works for them.
Interestingly, I still have most of my previous qwerty skills: If I'm touch-typing, I type Colemak. If I'm looking at the keyboard, I drop back into my old hunt-and-peck qwerty mode. Some of this is probably from continuing to use qwerty on touchscreens (where qwerty's scattered placement of common keys is somewhat useful).