I find the GoPro Hero too bulky. They are a very oddly designed shape. The Contour is what i would get persoanlly, especially as the helmet mounts mean you almost cant even see/feel the thing.
I do know what you mean though; we have often reached the end of a trail to find the Hero’s pointing up into the sky after meeting low braches! The Contour hasn’t suffered this as it has neater profile and sits at the lowest point on my lid, by my jaw.
Although a lot a people will buy them for use in/on cars, vehicles, etc so the Hero’s bulk isn’t really an issue for them.
The main issue I’ve noticed is, having to turn them on and then start recording separately – can be a faff when mounted to your lid and you’ve got gloves on!
The Contour uses one slide button for convenience – slide it forward, the camera turns on, beeps once and starts recording, slide it back and the camera stops recording, beeps twice and turns off – simple!
Most of my videos start with me looking at someone’s Hero saying, ‘yep it’s switched on and it’s started recording now let’s go’ as they’re not sure what it’s doing!
As for image quality, hard to say, both Hero HD and the Contours are very good, though the sound recording is better on the Hero. I think the Contour can suffer from a lot of wind noise – though I need to play with the wind cut level in the settings to see if that helps!?