My APC UPS has refused to use either of my small inverter generators or a car 12v powered inverter as in input. Just sat there on battery despite there being power going into it and other things on the same source running fine. Would run off another UPS tho which is weird.
When I finally gave up and got the big 33000w ozito generator, then it was happy enough to be on passthru power most of the time. It would click to battery everytime something else powered on briefly, and putting 2 UPSs on it made them basicaly ping pong around which was powered and which was on battery. They were both running tiny loads - one the router, adsl modem, small switch and a couple of NVRs in one rack, the other running the big POE switch and a baby NAS in another rack.
The 3300 is also able to run the fridge, which the small 700 and 1100 watt ones could not.
Its just noisy. really noisy. Like cant run it at night noisy.
Guess when all the long outages happen. Factor noise into your decision process. They spec it at 67dBA at 7 meters. That is insanely loud when put outside away from the house, and will really annoy those around you who are sitting in the dark and quietness of no power reading facebook on their phone screens.