One factor to consider with any generator is noise. How loud is it when it runs? Some are as loud as truck engines. Others sound like unmuffled lawn mowers. The quietest generator Diane and I have seen and/or used is the Onan QuietDiesel. When we run it and the Fantastic ceiling fan in the sleeper at the same time, the fan noise is louder than the generator. Standing next to the truck when the Onan is running, conversations can be had without raising your voice.
Generator noise can make a difference as to where one can be used without drawing unwanted attention or being unconsiderate to others; like in hospital zones, residential neighborhoods or parked next to a busy downtown city sidewalk. Reduced generator noise also improves the quality of life inside the sleeper.
Another feature that is well worth the added price is an option, available on an increasing number of generators today, that monitors truck voltage and automatically starts the generator if the truck battery voltage drops below a set point. In some applications, that option eliminates entirely the need to carry a sleeper-dedicated battery setup.