For the last five years I have been using a Sony Digital Camcorder, sometimes on a tripod held down in the rear seats with seat belts and bungee cords, sometimes sitting on the dash/held by pax. This is a 6 year old, "legacy tape" type of unit rather than recording to a memory stick. That means it takes longer to convert the films on the PC when I get home, and battery & tape life is only 90 mins, max.
The picture quality is superb. The propeller is almost invisible, sometimes showing up as a grey disk rather than the series of bent lines you get with solid state devices.
I have the camera connected to the intercom via a splitter lead and this is one of the deciding factors that you need to bear in mind as well as the lens type.
You MUST get a camera with an external microphone input. Throttling your intercom output is essential and provides hours of "fun" trying to get it right.
If I was was starting again, I'd probably buy the nflitecam.