I've been using the Drift Ghost for a couple of years and it's an excellent bit of kit for under £250. Perfect shape and size to mount on your helmet, the rotating lens is very handy and it has plenty of mounts available...the BIG plus is the 3 1/2 hour battery life.
Downside is the android app is pretty rubbish, being very laggy, luckily it's not really required that often with the screen built into the Drift.
For outright quality and mounts available you can't beat the Gopro..Trouble is the hero4black is now over £400...ouch. Also the battery life isn't great, you can buy extra for £16.
If i was buying one today I would seriously look at the new Sony X1000V or the AS200V..These new camera can rival the Gopro on quality and possibly even surpass it plus the added bonus of Sony's Steadyshot which for us bikers is an essential feature. Cheaper than Gopro, the only downside I can see is the battery life being very similar to that of the Gopro and that it looks like extra batteries will set you back nearly £40 which isn't so good. Cameras are due out this month, I am looking forward to reading the reviews to see how they compare. Oh yeah the Sony has stereo audio!
Plenty of footage on YouTube from the various cameras, just bare in mind that YouTube kills any quality with is compression. An uncompressed 30mins recording in high bitrate on the Ghost uses approx 3.8GB or storage.