main difference you'll be able to see is the wideness of the lense. 135 (contour) vs 170 (gopro). In a nutshell, the gopro is going to look more stable because it has a wider lense, but quality wise, the two are pretty similar. I find watching headcam footage from the gopro easier on the eyes because of this wide view. It mimics what i see out of my eyes, seeing all around rather than closing in on a smaller area
If you aren't solely mounting the camera on your helmet, the gopro will be more versatile and you will find yourself filming more and more with it outside of skiing as well