A complicated question indeed.
The Marquis Gold is Propane powered and will supply 5500 watts. Enough to run your 36 CKTS. Your truck bed genny????
You will have your genny available when the truck is not.
The weight of the genny in the front garage (belly is someplace else) is not all pin weight.
The genny is safer in the garage and protected from the elements.
It starts from a panel switch inside.
Not sure how you hook up your 50amp cord but if you cant do that while on the road then you cant cool the box down in prep for arrival at your destination.
Just some thoughts. The only bed mounted genny (gasoline) I have seen up close was rigged to plug in to a box added behind the pin box so it could be used in motion. He would crank it up about 2 hours from destination and it would be cooled off when he arrived.
If you need the genny for other things then you will probably be better off with the bed mount.
The recipe for perpetual ignorance is:
Be satisfied with your opinions
and content with your knowledge.