First. Be sure you are comparing Inverter to Inverter.. The Open Frame jobs are generally NOT inverter and not all enclosed are Inverter (though the non-inverter enclosed ones tend to be 1,000 watts or less).
When Champion first came out with Inverter generators they had some serious issues,, Typical of products from China, quality control was lacking.. They had to replace a rather large number under warranty..
That was, however, some years ago,, Since then they seem to be a decent product and I'v enot been reading a lot of complaints against them... Though I would recommend a Honda EU-2000i-Companion or a Yahama EF-2400i.. I can not recommend AGAINST the Champion or the Robi. Id just rather go with the quality unit.
Honda's do have one feature no other portable generator has (that I know of) and that is the Extended Run Fuel Tank... You see, to use that tank you need a fuel pump, Honda has one.. Others are gravity feed.