I've owned fifth-wheels and Class A MH's, but never a Class C, so I can't make a direct comparison. At one time, a Class C had the advantage of more sleeping capacity than a Class A, but that has changed in the last few years, since a lot of Class C's that had a bed in the cabover area now have a T.V. and cabinets, and Class A's now have bunkbeds.
I like the visability and headroom of a Class A, along with typically larger fuel, water and waste tanks, larger propane tank, more basement cargo capacity and a larger GVWR over a Class C. But, the Class C is a little lower in height and some feel that it is easier, or less intimadting, to drive.