I've been doing A TON of research because I cant decide myself, so I'm getting both the Contour HD 1080p(bike mounted) and also the GoPro HD(helmet mounted). I've been comparing footage as well. Here are a list of pros and cons for both.
Gopro HD
pros:
1. Uses standard SD cards, up to 32 gb
2. Waterproof, replaceable shell
3. way more accessories and mounting options.
4. Better audio than the ContourHD
cons:
1. 127 degree wide angle (that's a lot for me)
2. Lens is not rotatable or sightable
ContourHD 1080p
pros
1. Lens has a laser built in for alignment and is rotatable
2. 110 degree lens(not as wide as the Gopro, I think that's a good thing)
3. Has adjustable color settings
4. Lighter and lower profile when helmet mounted than the GoPro
cons
1. Only uses micro SD cards up to 16gb
2. Longer recording time than gopro(means more compression)
All in all, you're going to get better quality out of the GoProHD, but it's a wider angle. The battery life isn't as good, but the batteries easily changeable so you can carry a spare. I think the gopro could survive and accident better, or if it fell off your bike. If I could only get one, I think it would be the GoPro HD.