I have a Sony memory stick camcorder, the TG3E. The picture quality in flight is pretty impressive, and no problems with odd flickers from props or instruments. However, it doesn't have a socket for an external mic.
I saw a great in-flight instructional video where a little external mike had been popped inside one of the pilot's headset earcups. It worked great, because both ATC and his speech over the intercom were captured.
I'd definitely use a camcorder with that external mic. feature. It's inevitable that you buy dozens of gagdets over the years with features you never use and then when you want a specific feature.....