A RV of any type is not a financial investment. You're going to lose money.
It is, an investment in pleasure and happiness. We got great returns on our investment. :)
To answer your question, I have heard over the years that a C will hold its value a little better than an A.
Do they? I don't know. If they do, maybe it's because a C is easier to service than an A?
Or maybe, because a C usually has more sleeping space than an A.
Bottom line, condition is the important factor. And, depreciation is my least concern. I'll by what I like and suits us best.
It is an interesting question. Hopefully someone has a better response.