One thing to consider in your choice is the live view function. I'm not trying to sway you either way, both companies have sick options, but you might like one more than the other.
GoPro: LCD BacPac so you have a little screen on the back that allows you to get a live feed and check playback.
Contour: If you have a smartphone, you can sync it via bluetooth so you get an 8fps feed on your phone with which you can check the angle of your shot and change camera settings.