Never mind how today's Cummins's "Onan wannabe" generators are cooled, or oiled, or filtered, or how many cylinders they have ... how RELIABLE are they?
From everything I read, they can be good for thousands and thousands of hours. I believe that's the main thing I care about and what I think I mainly spent my generator dollars for when I bought the motorhome.
The problem with Cummins "MicroQuiet" noise and/or interior vibration is installation corner-cutting by the RV manufacturer. It's the usual story -> for a few dollars more manufacturers could use marine grade sound absorbing material all around the inside walls of their generator cabinets and high-quality vibration dampeners where they screw it down.
Honda's attempt at offering a built-in RV generator turned out being loud and not an inverter generator ... they essentially only made a half-hearted attempt at entering and staying in the RV market, IMHO.