I have both - along with a few others. I find I grab the contour every time I go to the track though. It's audio is quite good if you don't have direct wind blowing on it (mine is mounted behind the windshield) and its the easiest to use as you just flip the top switch and it starts recording.
Shape wise its small and mount wise - once you get to a std tripod mount, you can use Ram balls to ram mounts or panavise mounts. GoPro's record decently well as well, and they have a plethora of mounts. I find their mounts don't work well for motorcycles because anything longer than one pivot on their mounts vibrates way too much. So you're stuck converting it to tripod mount and then going from there. It's a good camera - just not my first choice as its a bit more complex to get recording than sliding a switch with gloves.
do you also have an ion air pro? IMO this thing looks the best of them all, but so far I havent found anyone using it? Any experience with this thing?