Excellent John. A very simple way to explain the differences of air bags to WDH. Basically the air bags adjust the level of the towing vehicle's body and does very little to share the load weight where as the WDH adjusts the angle of the chassis and shares the weight between the tug and the trailer. The only disadvantage of the WDH is during tight turns, the stresses placed on the tow hitch can be extremely over stressing the hitch and should be disconnected. This would be a good video to place on all the caravan forums for all to see.
Cheers
Merv