Short answer:
A class C is far safer, easier to drive, have more beds, fit more places, are easier (cheaper), to service and frankly less money than a comparable Class A. These points have been substantiated any number of times in many discussions on this and other Forums. Class A's have their plus sides as well like larger storage, towing capacity and... well that's about it. (just kidding) :B
Find the floorpan that works for you, A or C matters not. If you are shopping for a quality, lightly used motorhome (and you should be, but I digress), A or C there are lots to choose from.
For the record we are the happy owners of a 24' quality C (we sold our 22 TT and truck), and have not looked back. For our use no A could come close to meeting our needs. For many only an A will do so.
As always.... Opinions and YMMV.
:C