I do not own either brand of generator, I have a Generac 5500 watt open frame and an ETQ 1800 watt inverter generator. I cannot speak to most of your questions, but I can tell you that all engines, not just small ones, in all devices, not just generators, need to be run from time to time lest they become inoperable. The cylinders will rust if not oiled from time to time, the fuel systems contain rubber seals and hoses that will dry out and rot if not exposed to fresh fuel, in short, folks complaining that their generator won't start after a long period of sitting idle have brought the problem on themselves.
This is one reason lawn mowers are often hard to start the first time you run 'em in the spring, and that is often after only sitting idle for 3-4 months since last use in the fall. Let it sit for a whole year, and it will be dead, too.
I own those two generators, a weed whacker, a snow blower, a tiller, two chain saws, two lawn mowers, and three vehicles. So I made myself a log book to keep track of which ones I've used or at least run for a bit to keep 'em functional, and I make it a point to run each from time to time during the off-season even when not using it. Saves a LOT of headache, 'cause they always start when I need 'em to. And sometimes I find one breaking during the off-season, when repairs are cheapest and quickest (and I'm in no hurry, either) because nobody else is having their stuff repaired at the same time.