I chose class A over class C for multiple reasons:
1. When I go camping I like to see outside. Class C always felt very closed in because of the lack of windows especially on the front end.
2. When backing into a site, you can actually slide open the window and look straight down the side for a clear view in lieu of relying only on mirrors. Very important for overhead limbs etc.
3. Because of the large front window, similar to mirrors, it feels much bigger in size.
4. Class C's are much more prone to leaking, especially in the cab-over.
5. Driving and A is like looking out of a picture window. Driving a C feels like your in a cave with tunnel vision.
6. Class C's are almost at weight capacity for the frame out of the box. Class A's can handle much more weight.
7. Class A's tanks are usually much larger, see item 6 :)
To me a class C really shines when it comes to large families. You can fit a lot more people in a C than you can in an A.