Choice of towed vehicle (dinghy) is largely personal preference, constrained by the amount of weight your coach is rated to tow.
Check out the Motohome Magazine Dinghy Towing Guide for lists of towable vehicles by year.
http://www.motorhomemagazine.com/dinghytowingguide/
A lot more can be towed with some modifications, but the mods are usually $1000 or more.