5814 is a "special quality" tube, and rated for high vibration. It draws a bit more heater current but not much - 350mA instead of 300mA. My guess is a larger heater for longer life, and more mica supports for the tube elements, but otherwise the same mechanical design and probably the same tooling. It's rated for quite a wide variety of things, including channel balance - look up the RCA data sheet for more information than anyone really wants!
E80CC is quite a different tube, requiring twice the heater current and having 60% more gain - mu is 27 instead of 17.