Drift HD. I have an HD170 Stealth, love the quality and small form factor. Plus it's rugged as hell. I thought the Drift HD had the best color reproduction of the three.
I think the HD Hero/Hero2 color reproduction overcompensates a bit but the Contour definitely loses points for clarity. Clarity cannot be regained as easily as color filters can be added so the Hero/Hero2 definitely wins on quality. The Hero2 has a regular 3.5mm audio jack for external mics. I'd go Hero2 between the two but overall grab the Drift, either the HD170 Stealth or Drift HD Action.