I have this one. It has been good. I leave a 20 lb propane tank next to it.
Never ran pump gas through it, and don't plan to unless things get real wild.
From the 'Westinghouse' website.
"up to 7 hours on a 20 lb. propane tank"
That there's my problem with those things. On the larger units, you either have a garage full of flammable stuff (and in the case of gasoline, an age management problem), or you just get a short period before you're off to the races trying to find fuel. Naturally, there's some fuel to be saved with bigger inverter generators, at double the cost (also, the ones I've seen don't handle the throttle kick up very well in terms of power quality).
Our local gas stations tend to be offline in a power outage, and, of course, the retail places are completely out of butane, propane, etc. the instant there's a problem. JIT supply has it's issues. You'd be surprised how grouchy people get if there is some solitary place with fuel, their inner barbarian comes out pretty quickly. Of course, no power = no internet = no open for a lot of stores anymore.
During our last big outages, the fun part was watching the mayhem from people who ran their house propane down to zero (with no resupply in sight) and those with Powerwalls after they got a day's worth of comfort.
Really, there's no good answer, or everyone would do it. After a few week+ long outages, it becomes a kind of interesting intellectual problem.