not starting with pros and cons of SN and SM, just answering your questions:
* freezer: we have a waeco freezer in the cockpit locker, just next to the chair, works fine and is probably the only place in the SN where you can install one without major changes (~0,4k $).
* aircon: we have a portable seawater cooled unit but used it only 4 times in the last 5 years. Italy, Trinidad and Panama in the Marina (and have been very glad we had one...). There would be space to install a small fixed unit on starboard opposite to the front bath-room, -3k $
* generator (eg. fischer panda 4000) can be installed in the engine room or (as we have it) in the aft locker.
* water maker: can be installed in the engine room, the tubes below the cockpit locker. enough space for 2 ore more (thanks Ian, that was really a very good hint), control box below the galley, no additional through hulls necessary. ~4k $
KALI MERA, SN120, Mazatlan