Not much difference in any given price range. The more expensive models generally have somewhat better materials, e.g. better grade upholstery and flooring and cabinetry, which helps in the longer term. The quality of the assembly of any given RV is hit or miss - the quality control (consistency) in the RV industry is poor across the board. And nobody provides a credible ranking system, so you can forget most anything except anecdotal reports.
For a Class C, I would probably lean toward Winnebago/Itasca as the best bet. Their build quality is decent and their customer service and parts availability is good.