There is no quality issue directly related to the classes of Motorhomes, rather the classes of Motorhomes refer to the body style.
Basically there are three classes: A, B, and C.
The Class A is the type that is on a truck or bus chassis and is characterized by its bus like appearance. The larger of the Class A’s are called Bus Conversions and resemble commercial type passenger buses. There are Bus Conversion owners who don’t like there coaches referred to as Class A’s.
The Class B Motorhome is the conversion van type and the Class C is the type that has the coach area integrated into a truck cab type chassis and has an overhead area above the passenger cab. Looks like a van front with a camper on back.