...it has to do with the fact that butane/propane-driven fridges are not allowed to tilt more than a few degrees from vertical. So, at least under sail, they cannot be used.
Apart from this I don´t know any problem., But I can imagine some cheaper caravan-style fridges might be big electricity consumers.
The problem with normal house hold style fridges is that they need to be still and upright or the gas and liquids in the system mix. This is why you must never lay a fridge over on it's side or it may not work as well.