As has previously been stated, they are so different it really comes down to your needs. I had a class C for many years and loved it. When I moved up to the class A it was primarily for the capacities. I now carry 100 gallons of fresh water for extended stays while dry camping. Many class C's are nearly at weight capacities before adding all your gear and filling the water tank and you didn't mention if you were planning on towing a vehicle.
It is true as to the cab being built by the truck company versus the RV manufacturer, but I haven't experienced any issues. I can also easily swivel my front seats so they are not just wasted space when I am camping. This can be done in some class C's but is the exception rather than the rule. Even in the class A category their are many differences between the F350, F450 and the F53.
It all comes down to what you want and how you plan to use your RV. That is why they build class B's, C's and A's. Although they have similarities, they serve different needs.
Good luck on your decision.
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