I use a Go Pro 3 and a helmet mount. After some time trying that I would recommend a chest mount.
The angle from the helmet fore shortens the view and makes the perspective look odd. You don't get a true sense of speed and distance.
It also tends to "fire hose" the view. That means the camera goes where ever you look so the image bounces around.
Some people mount to the bars but then you just get a look at the road/trail ahead, with no image of what you are doing. If you look at some chest mounted video you see the hands and bars reacting to the terrain.
Another thing to consider is editing your video. Some people just turn the camera on and post a 30 minute, one perspective shot of the ride. Interesting to the rider, because they relive the experience, but youtube data shows most viewers drop off by 3 minutes unless something grabs them. I've made a number of diving videos and studied that a bit. If you can edit it down to that time, and/or add some other angles/perspectives, it becomes more watchable. I just edit in microsoft moviemaker (because I know it) but there are other editing platforms.
Here's a couple of videos. Helmet cam angle in the first two, various angles in the third. One is short, the other is ten minutes and the last is 6.5. You can see how the second drags on but the third is better because of editing. Cheap camera, basic software.