I installed new ocean breeze units that they custom made for my dimensions and inlet/outlet and piping configuration I needed. The whole thing is made form stainless steel (I think 316) so nothing will rust. I got the soft start installed and my 18,000 btu/hr unit will start on a 2,000 watt habor freight inverter generator running in eco mode.
Lots of self contained units are junk, especially the ones made by the big brands. They use painted steel that is going to rust away.
The self contained has all the same components as a split unit, so as long as they use quality components, there is not much of a difference.....but it all depends on the maker.
In my 41c, it was refit before me and there is a unit in the salon 18,500 btu/hr(port side, with a small bump out enclosure) that also feeds the master stateroom. In the forward Vbirth bunk, under the stb vberth is the other unit 12,000...it also feeds the galley.