Eh, I'd say it kinda depends, Colemak focuses more on rolls while Dvorak focuses more on alternating between hands. Though I think that Workman is a superior alternative to Colemak when it comes to ergonomic rolls.

Xah Lee wrote an analysis on why he believes Dvorak is better than Colemak: <http://xahlee.info/kbd/dvorak_vs_colemak.html> and he brings up the frequency of the "th" digram, which on Colemak is a bit of an issue due to the finger travel.