"The higher rated hitches (10,000 lbs) were found on MH's with additional HP and the Allison 3000 transmission. "
Don't just go by the hitch rating! My coach has a hitch rated for 10,000 pounds but weighs 22,000lbs dry and has a GCWR of 30,000lbs. By the time I load it for a trip it is generally pushing 24,000lbs so the most I can pull and stay under my GCWR is 6,000lbs. The limiting factor on mine is the transmission. For some reason Freightliner only puts an Allison 2100 in most coaches that are only 35ft long (208 inch wheelbase). Go up a foot and you get an Allison 2500, 10% more power and a much better tow rating but still not 10,000lbs the way I figure it.
My coach was actually advertised as having a 10,000lb tow rating even though the factory engineers denied it. The engineers finally made the marketing people take that off of the add. Just because you see it advertised doesn't mean that it is true.