We elected to go with the Dometic Brisk AIR II air conditioner for a couple reasons:
1) I only intend to do a single air conditioner on the Airstream.  So, I knew that I wanted a 15,000 BTU unit to make sure we could keep the whole thing cool. 
2) We're trying to keep the Airstream really light. The more weight, the less fuel efficient our tow vehicle will be.  Further, I like the idea of being able to tow with a small SUV (Jeep Grand Cherokee)
3) This Dometic unit has a nice thermostat unit that I intend to use with it. 

So, we went with this unit.  It should be here in a few days.  Since it's 9 billion degrees in the storage unit, don't be surprised if this is one of the first things that I install.

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