Upper deck 747 feels much more spacious and is generally quieter than 767 C Cabin. Even if the narrower seats on 767 don't concern you physically, you are actually in closer proximity to your seatmate - and it does feel noticeably tighter IMO.

Oh and for some reason I always seem to get a dry throat during a 767 flight! Never happens on other UA craft. Is there a different air filter system or something? Or am I just weird?