A lot depends on how you plan to travel. If you want to drive to a single destination and stay there for a few weeks and then drive home, towing a vehicle with you may not be economical, unless you already have a vehicle that can be towed 4 down.
If you plan on visiting many of the sights, over the span of several months, than I feel a toad is essential.
It also depends on where you plan to go. Not all destinations may have convenient car rental facilities. Large destinations will be no problem, but some smaller, less popular or more remote locations, may not have cars for rent.
Then you have to figure the size of your coach. Obviously a smaller coach will be able to travel on certain roads, and fit in to parking areas for restaurants, that a longer coach may not. There are just way too many variables and there is no right answer without knowing all of your travel plans, family size, and expectations for a specific trip.