HD webcams are good.
With music videos, sound quality is the important factor. A grainy, lowlight picture often has more character and vibe to it than a really clear pic. HD gives the best format, hence advocating an HD webcam - like the Logitech 1080p (which has decent sound too).
A cheap, good band result is often -as with Cover'd s - miming to the recorded track.
If you use a click track - or just take care with tempo, you can often get away with filming a live gig then using the recorded track. Just need to take enough pics that don't show lips or fingers, and cut it back to the drummer hitting the hi hat in sync.
BUt camera quality is irrelevant as the pic quality is less important than the sound, and unless you've hooked the camera up to the desk, it won't be good enough, and even then the mix will be not be optimum for the film, even though it might be great for the room....
Finally.... I'm going to try setting up a whole load of webcams on the lighting poles for a multicamera live gig shoot. They're wide angle, and if the shot doesn't work because people move, there will be plenty of other shots to cut to.
This vid of my covers band, was shot by the roadcrew with 3 professional cameras and a multitrack recorder from the desk which I mixed afterwards. With hindsight I'd have mixed in more of the rough camera sound, and set up mikes pointing at the audience, to give it more of a live feel. It was hard syncing sound with pics - and you can see. (Spot the change of drummers... one of the roadies likes to have a bit of a bash...)
[video]http://www.bashband.co.uk/hearus.html[/video]