Buying an older class A (or C) is not for the weak of heart or budget. The "quality" of one brand or another has to be determined inside the era they were built in, and the original market they were targeted to has to be considered, also. Aside from brands and manufacturers building to a price and a market, which a bit of poking around and asking the right questions can answer; when you buy an older RV you need to be looking at overall vehicle condition, mileage, vehicle service records, vehicle completeness, and past owner "upgrades" and modifications.
Also consider this, by the time you buy a 20+ year old RV, any of the build quality issues a rig may have had, have probably been addressed by previous owners. Buyers of brand new RVs not only take the depreciation hit, especially if they trade off the rig after a few short years, but they are also the ones that go through all of the shake down activities which most new RVs inevitably go through during their first few years of use.
I think it highly unlikely that you'll find a bone stock used RV of any class that is over 5 years old. Because an RV is a rolling home, people do things to them like they are a home. The used unit I purchased last year certainly did have some prior owner customization, some of these changes were good, some not very well thought out. I also discovered a lot of deferred chassis maintenance which also falls into the category "what does the previous owner care about"
As you get used to your new-used RV you learn what the previous owner cared about, because that will be the stuff you see having been addressed by them as the vehicle got older, and you'll encounter the stuff that needs to be fixed or maintained, and this was something they either didn't care about or weren't paying much attention to.
In my case the previous owner had done a good job of maintaining the house. Cabinetry and upholstery was in excellent condition. Plumbing was good, along with having a new kitchen faucet, new water pump, and all the bits and pieces of the house were in good working order. On the other hand, while the chassis looked good and mileage was pretty low for the rig's age, there was a lot of delayed chassis maintenance, including a desperate need for new brakes, plus a bunch of stuff under the hood that started to fail as we started to put some serious road miles on the rig. Think radiator leaks, old hoses and tubing that were checked and starting to ooze and leak, and don't get me started on marker lights which were just totally worn out.
Try to get the backstory about the rig from the seller. If nothing else, when your new-to-you rig has maintenance needs, at least you might be able to correlate it to the story of the life the rig had before you purchased it. In my case, the previous owner was the second owner, he purchased the vehicle when it was about 6 years old and had about 30k on it. The first owner was a real road warrior and put a lot of miles on it in a short period of time. The second owner was a weekend warrior and the miles it accumulated in his possession, close to 20 years, were to and from home and nearby camping and outdoors stuff. It never really went on long trips with the second owner. This partly explains the deferred maintenance as the second owner wasn't driving far enough with it to really be bothered by stuff that might have been degrading on him, like brakes and hoses. He just kept the liquids topped off and went out on the weekends and had fun.
Anyway, this is a long ramble, but I think it kind of addresses your question, by saying, the prior reputation of a manufacturer may not be all that important when buying a used rig if your inspection of the used rig, or the inspection of an "expert" you bring in, shows that the rig is decent enough and worth what the seller is asking. Oh, and be prepared to do some maintenance no matter how great the RV may be.
