Look at this thread: http://www.airforums.com/forums/f463...emi-66408.html
The 2012 should be basically the same as the 2009 through 2011 models. If you are towing, you will want to have the truck in the tow/haul mode, which deactivates the shutdown to four cylinders function. With your 19' Globetrotter, I think you would be happy with the 1500
. We are very pleased with our crew cab 2010 model pulling our 20' Safari, which is probably heavier than your AS. If you tend to carry a lot of weight in the bed, that would be the only reason that I could see going to the 2500 over the 1500.