As most seem to have alluded to, the brands may not be terribly different in that they all buy similar style frames, use similar materials for their construction, and have basically the same appliances and systems.
Similar price points across the brands under these circumstances should yield similar quality levels.
Some may do one part of the process a little better than another, but overall they should even out.
What does appear to change in quality is support. Some brands seem to have a markedly better reputation for how they back up their products.
Thor as compared to Winnebago or Grand Design as compared to Forest River for example. But even here, you will find some folks who have had experiences outside the wider experiences you hear about.