Martin, I can relate my experience and opinion on the air conditioning on my 54. I am not interested in entering into a debate but offer my opinion only.
Four years ago I replaced the a/c in the main cabin with a unit from Flagship Marine from Stuart Florida, on recommendation from a trusted friend. The unit is terrible. Too noisy, much vibration, it cycles and you hear the loud on and off of the compressor, and related to the limited ducting, there is not enough air flow to cool well enough. I often do not run it because it is so annoying.
This past winter I was In Martinique and the day before my scheduled departure the aft cabin unit failed. The salt air had rotted the fins and the gas leaked out, it was trash. The local provider, Caraibe Marine, had on hand a unit and installed it in my time frame, so there was no shopping for the right unit, I bought what was available. It is a Frigomar, self contained unit referred to as the inverter series. It is the BEST! Whisper quiet. It is powered by the 230 volt already there, 50 or 60 Hz., but the fan and compressor both are DC variable speed drives, so no noise and no large current draw at start. It starts very slow and quiet, ramps up to what is needed, can cool the aft cabin so you could hang meat.
I like it so well, if I were in a place where I could have it done, and cost was no object, I would replace both the other units with like systems.
It does include heat pump heat. I have never used heat on my boat as I have always been in the tropics, so I can not comment on the heat.
I would be happy to answer any questions if you want to email me direct.

Bob Hodgins
Gallivant
Amel 54 #31
currently stored in Raiatea, French Polynesia