One thing I've found on these boards is that the perception of what is "quality" encases a wide, wide range of criteria. What I may consider a quality build, another may consider cheap junk, etc.
With that being said; Winnebago produces an RV, Vista/Sunstar, that is (in my mind) a notch below Newmar and Tiffin's bottom end coaches. That is, a notch below on price point, btw. I don't necessarily think the Vista/Sunstar fall a notch below on build quality (many will argue this), but definitely a notch below on component quality; plastic sinks, cutout bay doors, etc.
So, a part of the perception of Winnebago, as a whole, possibly gets a little skewed because they choose to produce an RV at that price point, while Newmar and Tiffin have shied away from it. Dunno.
From my perspective, when comparing price point to price point; Newmar, Tiffin, Winnebago, and Fleetwood, all produce somewhat equivalent coaches when it comes to build quality. Again, you will see tons of arguments against that statement. Those four brands (again, my opinion) are head and shoulders above the worlds best-selling mass produced junk I have been inside in the last year.
And of course, whatever brand you own is the best on the market.