They work fine but the 2 hose ones are much better.
The single hose units pull air from inside the space to pick up the heat and exhaust it. As a result, you are constantly pumping some of your cooled air out of the interior. They still work, just not as good.
The dual hose units, pull outside air for this purpose, so they keep more of the cooled air in the interior.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV