I have the QD3200 in my unity. I have gone to several shops and it is hard to find service, so after some research i did track down the actual engine, which is made by Hatz. If you ask for Hatz parts you can find them. It is a simple air cooled engine, nothing fancy in a green onan box.
It is pretty loud and you cannot sleep inside with it going and the AC going.
The Hatz tech said they are cold blooded, and smoke until they warm up, and even then mine does have some visible exhaust. Kind of embarrassing, so i take a honda 2000 and shove it in the woods when i am with a big group.
So if you want to turn on for 10 minutes and toast some bagels, or microwave popcorn, the propane is a much better choice. If you want to run the generator for hours to keep the ac on for dogs or other long power needs, then the QD3200 if probably ok, as it does sip fuel.
If this ever dies, which the tech said doesn't happen, i will weld a custom tray and put my converted Honda propane 2000 on a slide out in the hole for making toast in the morning.