The VoldR models, IMHO are the best. They are low profile, supports a 16GB chip last time I checked which is good for 8 hours in HD mode, and 16 hours in SD mode, and the batteries (cell phone style) are good for about 2 hours in HD mode. I bought some extra batteries, 4, so I have 10 hours of video recording capability. The newest models are 1080p, as compared to my 720P. My 720P takes great video.
Check the chip size and record time against the Go Pro. Last time I checked the Go Pro only supported 2GB chips, and have heard complaints from owners that it eats batteries.
On the VoldR, in HD mode the field of view is 130 degree's, in SD it's 90 degree's.
Originally I was not happy with the sound, it was way too sensitive, but, since that time they had a free down load where you could set the gain on the mic, and UHE member Kzoo has one and is super happy with his. So, I'm assuming that the newer models come with the software to set the gain on the mic.
In use, the VoldR has an on/off switch that is a slide bar that locks into position when moved, is very glove friendly to use, and gives you a beep, or a double beep indicating that you have selected record or stand by.
The other great thing about the VoldR, is the laser dot aiming system which is very helpful when setting up your camera on your helmet. There are two laser dots that you actuate and indicate the center of field of view, this is a great feature.
I have about 30 hours of recording and in all that time never once has the image "ghosted" along the sides.
The VoldR's mounting system is a kind of a break away with a leash, so when you ride under a low branch and it does get hit, it will just get knocked off and dangle on the leash until you remount it. It seems to me that the Go Pro sticks up like a weather vane, and would be hard to get your goggle strap over, and would really be prone to getting whacked when riding.
I spent a lot of time looking for the best helmet camera I could find and I think the VoldR brand is it.