Richard, just a couple of thoughts to flush out the discussion a bit.
"The water pump systems are generally less efficient in warm water than air cooled and destroy the energy advantage of the of the variable speed compressors."
I''m not sure about the last statement as I have not yet used a variable speed compressor. However, for systems without these compressors, I doubt water cooling is categorically less energy efficient as that would depend on the draw of the water pump vs. the additional cooling value of water over hot tropical air. My experience suggest water cooling is going to be measurably better. I''ve also watched others experiment with water cooling in their boats (we had quite a group doing this down in Trinidad) and they found the same results I did. Insofar as ''reliability'' is concerned, I suspect your view on water cooling being less reliabile is drawn from so many systems using raw (salt) water, which does indeed bring aboard a lot of compromises. In 10 years of water-cooling reefer use, full-time, we''ve never had an issue with the water cooling feature because there really isn''t anything to go wrong unless the pump breaks. (I lied there... We need to clean the screen filter occasionally.)
I completely agree with your two main points stated upfront, and everyone reading this thread would help themselves by pondering them: everyone has their own preferences re: refrigeration (some want a meat locker!) and different boxes (and I would add, boat electrical systems, and lifestyles, and the waters in which the boat is used) can all be better or worse candidates for a given reefer system.
I can''t speak to your comments about Isotherm having no interest in after-sales service, except to note that it''s dealers who must provide service and dealer performance is so varied in quality and availability that probably any general comment is going to miss the mark. You may believe Isotherm is intended more for boats in cooler climates because they are a N European company and have deep market penetration here...but we saw excellent service from our Isotherm unit for 4 years in Florida and 2 in the Caribbean, so I''m not sure what else to expect of a system that our Isotherm system isn''t providing.
Just more food for thought... No simple, black & white answers (or even questions) here!