Definitely the Roam.
I have a Contour Plus, mainly because the Roam was released after I bought the Plus

, although the Plus is a better camera overall, but not worth almost £300 more than the Roam.
The main competitor to the Roam is the
GoPro Hero HD2, an excellent camera.
It's disadvantages:-
1) it's not a great shape especially when attached to a helmet,
2) you have to use the waterproof case even for very light rain/mist, the waterproof case has a steaming up/fogging problem,
3) unable to rotate the lens to ensure it is horizontal,
4) the Contour produces a better video image, except in low light conditions.
5) It's more expensive, the Roam being better value for money.
It's Advantages:-
1) 170 degree field of view even in 1080p mode,
2) WVGA at 120fps, great for slow motion,
3) Can change all settings without needing to connect to a pc.
4) Excellent low light performance, far superior to any Contour.