The biggest complaint you will hear about a Champion synchronous generator is the fact that it is louder than the inverter generators. Champion customer service doesn't a lot of complaints either.
We became the third owners of a well used 3500/4000 3 years ago and even though it looked beat up, it started with one pull until this year when the recoil started failed. I wanted a upgrade so I gave it to a neighbor before finding out that a 3000w inverter wouldn't handle the altitude as well. Now I have a shiny new 3500/4000 with remote start and a happy neighbor too.