For the record Honda's have 1.5 special features the others lack, NOW this is only important IF they are important to you.
First the 0.5 The 2000 companion. it has a 30 amp outlet (usually 2000's only have 15/20 amp outlets) and thus when paired with a regular 2000 (or another companion) it uses a lower cost parallel kit.. I call this a half feature because the Regular 2000's With the more expensive kit.. the 30 amp outlet is part of the kit.
The real feature is a genuine honest to engineering fuel pump. .What this means it it can not only use the gas that is in the on-board tank but it can "Suck" gas out of an "extended run" tank. I have no clue as to how big that tank is (Please use the genuine tank not a home brew) But if you need to run for say 20 or more hours like to keep the wife warm when the power company fails (Been there. Done that, used the motorhome's ONAN) well that can be a REAL feature.