I agree that water cooling keeps a more controlled environment for machinery to operate. Of course, the "greenies" have forced much of that upon us. The K does have an excellent cooling system, but a water-cooled engine's cooling system is under a lot more stress to maintain consistent cooling. Driving through desert parttime is no big deal for the K, but for long term reliability IF I'm living in such an area, I'd much rather have an air-cooled engine... no mechanical cooling system to break down, no hoses to check, no electronics/fans, no coolant to replace, etc etc. The currently-engineered air-cooled engines have no difficulty with 30 or 130-degF temps. 2 radiators on a K: coolant & oil; only oil on an R.
There is another major maintenance point (seldom considered) in the K for desert areas where there will be a significant amount of sand/dirt --- the air intakes up front & filters. I live on the coast and there is so much fine sand on the roads you cannot see, but it loads up the filters faster on my K13S than it did on my R12R.
Long live the air-cooled VW's!!! One other note, synthetic lubricants really prove their mettle in air-cooled engines. Good luck with whatever you choose.