Were I recommending a full time rig, I'd probably go with a class A rig over a C because there is more room inside, and usually more available space in the outside basement storage. Unless the class C has a fiberglass nose cap which protects the seams from water, it likely has water damage.
Of course, class As have their tradeoffs, such as finding a place that will service them, but nothing is perfect. The advantage of an "A" is that gassers on the Ford chassis give you a lot of bang for buck in the used market.
Just be wise and watch stuff that can cause leaks. If you are looking at used rigs, and you see bubbles, discoloration, mold, or other issues, run. You can get a drivetrain rebuilt for less than it costs to rip out the interior and replace rotted items.