Yes I will agree that a normal camera will have a better picture, well what do you expect? It has better processors and should have a higher quality lens. However unless this guy is making a DVD that will mean squat to him. However just because something is better doesn't mean the other thing is crap.
Some of the Sony CCD cam's recording onto a digital camera have a good quality picture with 480 Scan Lines.
Also the twenty20 helmet cam is excellent quality, I have seen amateur videos with a mix of digital video and helmet cam from one of these and the change in quality is not noticeable unless you try to look for it.
http://www.twenty20camera.com/helmetcamera.php
You say I don't know what I'm talking about, I say I have done runs with a normal digital camera stuck to my head and a bullet cam stuck to my head. Want to know which gave the better video? The bullet cam, the big camera made me feel weird as I rode, the footage was more rocky and bumby because the camera moved more on my head. I still say that the best quality helmet cam video will be a good bullet cam. It allows you to ride better, the footage is better.
Want to know something, when you see helmet cam footage in a bike video, they are not riding around with a normal camera strapped to their head. They are using the highest quality helmet cams you can get or they are using those look back cams, which are effectively a hibrod between a bullet cam and a digital cam. They pretty much look like a TV remote control.