I have had some experience with water draining from the A/C so let me give you my 2 cents worth.
I have had 2 Airstream trailers and now have a Motor home. My first trailer had a Coleman unit replacement. Water ran down the side.... Right over one of the windows. Not really an issue just an observation.
My second trailer still had the Armstrong unit, plumbed through the skin to drain on the ground. This was my first experience with the detail of thought that went into the Airstreams. Unfortunately the Armstrong died and we installed a Coleman with a heat strip. Again we had the water problem, but now it went over the vista views and a window and eventually down a curbside awning.
I personally think the drain is an elegant way to move the condensation from the roof to the ground without leaving any substance on the surface of your trailer.