pros and cons to both equally... I like the gopro for its indestructibility , honestly, theres vids of it being dropped from 30 000 feet and shotgun blasted from 10 yards and its still fine...
I used one of the 3m mounts on the side of my gun like this
it can easily detach, and at night time when using a IR light it acts as night vision (when you buy the screen attachment like i have) ... does it film the best stuff from there? no ... on a helmet it sticks out like a sore thumb, the contour is the way to go for helmet footage... which is the best type of footage i think