After using the Contour HD all year I think it's better than the GoPro. It is much easier to use, has better batter life and takes better quality video. So I say go with the Contour.
Do you have a lot of play between the shaft and gear? If the bushing is worn out it will cause the gear to kick the clip off the shaft. I've had it happen. You need to press in a new bushing, use a new washer and a new clip.