They put 4k generators in most motorhomes with a single air conditioner for a reason! Those that have never owned a 4k Onan need to try one, you'll like it.
Now to travel trailers, the Honda 3k or the Yamaha version is as good as it gets. The twin Honda's or Yamaha's are the newest fad, but you get what you pay for in generators.
I have a 2k Honda and a 3k Honda and if pressed to sell one or the other, the 2k goes. I also own several other generators and none come close to the Honda/Yamaha for reliability.
Don't skimp on generators anymore than you would tow vehicle and you'll never regret it.