I have both, the £42 K-Edge and the standard £20 handlebar / seatpost GoPro mount. The K-Edge is good, very solid, can mount the camera above or below the bar, but thats it, but when its mounted its very solid. The GoPro mount is good too, obviously you can mount it on the bars, in the same way, above or below, but you can also mount it pretty much anywhere else on the bike. The seatpost, downtube, forks stanchions (I have Pace rigids so can get away with it), fork crown etc, very versatile.
The K-Edge mount def looks the best, but If had to buy just the one, I’d buy the GoPro mount, there are simply more options to mount the camera, and in my opion the better angles of filming make for better footage, the standard POV gets a little boring.
Hope that helps.