Our Dometic performs perfectly well in most cases, especially considering
its thin wall construction and the fact you have a tiny furnace cranking
out BTU's right up underneath it.

 One thing that is easy to figure out is that you absolutely don't want to
depend on it to perform at peak efficiency inside a closed up bus.  You'd
be lucky to keep it under 60° inside.  We have BTDT, resulting in warm soda
and beer.

  In a half hour last week, I left home reading 80° on the dash in the
shade, then saw 117°  in a 15 minute Trader Joe's visit.

  As for which mode cools better, when I am plugged in, I turn the
thermostat _all_ the way up.  Overnight, a thermometer set on the top shelf
on the right side, will generally read 29°.

  If I can't plug in, running on propane the pointer is set horizontal
(pointing to 9 as on a clock) or even lower to achieve 29-32.

  Daytime summer camping with doors open in shade, the box will generally
run slightly above 40.