I got the full foam option with my Marquis Everyday 660. While it may be true that the milder climate means less benefit from the full foam, we in the LA area suffer some of the highest marginal KW-hr rates in the nation (.39 in my highest tier, IIRC). So, the cost of inefficiency is big in this area.
Secondly, I have read that the foam actually serves to provide stability by restricting movement of the internal plumbing and may actually help to prevent leaks. I guess it makes sense that it might reduce vibration around the jets and their plumbing joints.
I had a Sundance for over 20 years that was fully foamed and it never had a leak until its end of life. Because of other failures (heater/pump and/or control panel) I never started troubleshooting the leak.
From what I understand, it isn't all that much harder for a pro to troubleshoot a leak in a foamed spa. For me, exposing the sides of the spa will be a bigger issue if that happens as I have mine buried in a deck.
lol your evaporation of water comes from not sealing it with a proper cover and that is a fact! The problem with full insulation and I cant believe anyone is doing that anymore i KNOW PL (Premium Leisure) doesnt for sure (i go to that factory) but sounds like the R factor is important due to your high energy in LA (i dont live there so I dont know) The problem with insulating is if you spring a leak it will be a mess and time before finding it. This is the MAIN reason they are insulating before plumbing spas. I know these other comments are great from very skilled men but I know what I am talking about too I been doing this for 7 yrs and seen and heard it all. Food Color ever so softly in the water in front of each jet without making a ripple in the water to determine where a leak is (ever so gently!)
Jen