There are 2 reasons I chose to recirculate rather than creating an air intake. First off it was much easier and less invasive on my camper to recirculate the air. The already is one large hole in the floor for the hot air exhaust. I didn't want to add a second. Also the way the unit is set up the intake air is brought in through vents on the top and both sides of the unit. To cover all of those and vent them in a already tight space would not have been easy to accomplish.
The secondnd reason is one that was just mentioned. I think it would be more efficient to cool off the already cool and dryer air then bring in hot humid air from outside. The recirculating air in a car analogy fits my thought process. I may be wrong in this but for now I'm happy with the results