Calderas full foam is like other high end lines, D1, Sundance, Hot Springs, Jacuuzi to name a few.i personally like this form of insulation better.( there can be a huge debate on which is the best) i am not going there.
Emerald uses what they call a three levels of thermal protection
1. polyurethane spray foam on the shell,
2. ultra foam spray over that.
3. air space
4. Reflectix heat shield wrap on the inside skirt panels
Both ideas are trying to accomplish the same thing . heating efficiecy. the full foam method is to insulate the cabinet with the lines in them, no heat loss. the thermal chamber is using the secondary heat of the motors to circulate the chamber and keep the pipe warm.. again i am not trying to get into the discussion on the forum of which is better. though i have my opinion and other guys on here have theirs.
I sell both styles and i personnally like the full foam style.. I see less issues out of our store between the 2...
Hope this helps,I don't think you can go wrong with the Caldera. if you like the spa, like the dealer go for it.......if your happy, were happy to help