Depends a bit your RV and what you expect out it and who is going to run it.
We have a Honda 3000is for our house as a back up. It has electric start and is very quiet. The draw back here is that it is very heavy.
For our 5th wheel I wanted something that is lite, easy to run and easy accessible so my wife could start it without having to lug it around. Running the AC was also a requirement.
We opted for a EF 2400 isHC Yamaha.
It is only about 70 lbs, quiet and reliable. It runs everything including the AC.
We had a generator box custom built
to fit the generator and installed it on the back bumper. To run it we just open up the main door (can be used 1/3 open if raining) the air intake door and exhaust door, start it up, and plug the cord in around the corner.
We had to extend the rear bumper
to make this work. It all runs fine, we did Yukon and Alaska last year for about 3 months. Very easy to use, but a bit of extra cost to have built and installed.
This works very well for us.
Cortes Island, BC. Canada
Pony: 2008 Dodge 3500 Laramie, 4x4, Quad Cab
Harness: Hijacker 24-AS-18 Autoslide, Demco Glide Ride Pin Box
Chuckwagon: 2011 Rockwood 8265WS