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).