We chose a C over an A because of the extra sleeping space, the ease of service on the chassis, and the crash safety for the cab. What I didn't ever see considered before is the ease and availability of body work.
My parents have a 12 year old class A and someone stopped short in front of them in May and their front end is smacked up, window broken, etc. It is mid July and they're still messing around with the insurance company trying to find out exactly who will repair it and what will be done since the front end will either need to be fabricated or salvaged off of a donor vehicle if they can find one. I have to think that our plain old un-sexy standard white E450 body panels are a dime a dozen and we'd be long back on the road by now if it had been our C.
Our passengers move about the cabin when deemed relatively safe (I know it is truly never safe), so I don't really know why that would be different between a C and an A.
Another thing that we like about having the cab is that we use it for storage when we're at our destination. We have a curtain behind the cab for privacy when we're stopped for an overnight, but we use a windshield cover when we're at a destination. So the cab essentially becomes out of sight storage for us between the two. A nice place to put collapsed dog crates, a bin for shoes, etc.