I think the real advantage is 1.) Speed (very slight advantage) and B.) the ability to have fairly level dry ground always.

I think about the camping I did last year and it would have been perfect. But I was not with a family and I was camping in an area I was unfamiliar with.

One huge downside is that they are heavy. Putting a couple hundred lbs on top of your roof really makes a difference in your vehicles handling characteristics.