I second the recommendation for Colemak -- they put a lot of thought into analyzing letter patterns and key positions. Colemak minimizes finger movement off of the home row, reduces same-finger key repetition, and tries to balance left vs. right hand use. They also kept certain common application shortcut keys (ZXCVB) at the same position as QWERTY to ease learning and maintain certain muscle memory actions. Check out their FAQ: http://colemak.com/FAQ
I'd also agree that the comfort aspect is much more important than raw speed. I can type slightly faster on Colemak than I used to type on QWERTY, but after I switched, I feel far less fatigued by long typing sessions. As a developer, I figure I'll probably be doing a lot of typing on keyboards throughout my life, so I should do what I can to ease the negative impact on my wrists and fingers, etc.
If OP has already invested time learning Dvorak, maybe that's the way to go -- either one will be better for you than QWERTY. The hard part is setting aside time to learn and transitioning. At first I tried flip-flopping back and forth (what with having a job that required typing and all), but I ended up not getting better at Colemak and actually getting worse at QWERTY. After 2 weeks of dedicated practice and lots of typing games, I could slowly type in Colemak without making a huge amount of errors, and after about 6-8 weeks I'd say I was proficient and back at my normal typing speed. That murky time at the beginning when typing productivity drops can be tricky to manage, but it's definitely worth the effort in the long run.