Just a guess here, but I would guess that with the5th wheel, you have more contact area at the hitch which would evenly distribute stress across the entire pin box. With a gooseneck adapter, all the stresses would be concentrated to the pin only. Again, just a guess. I do know of several folks around here that use the gooseneck adapter and love it. I help set one up with the guy that bought our old 5th wheel. I like the idea of still having some bed storage while hooked up. My hitch is a Reese, and it takes up a lot of space.