I'm a class A guy and so are the people I tow with. My friends who have a Ford chassis have had nothing but probs. 3 of us bought V10 Chassis, all three blew spark plugs and had expensive repairs. Two of us bought GM 8.1/Workhorse class A, and are loving it.
The ford in Class A is actually rated higher for gross weight, but I've never had a prob out pulling them, especially over grades, and getting better mileage.