My view is sometimes considered snobbish, but that is not what drives it. The RV business is extremely price-competitive, so if you see two coaches that appear superficially the same (amenities, size, etc) and the MSRP price differs, even 1%, you can be assured that there is a difference in the construction and quality of materials. Probably under the covers, so you need a good eye for detail and careful attention to specs to identify the differences. Maybe it will be something you don't care much about, but you need to figure it out. If there is 5% or so difference, there is probably a lot of difference. Note I said MSRP, since used prices can vary widely. The NADA RV Guide will give MSRP prices for each model, so you can use that to gauge the price class the coach was in when it was made.
Some things that lower-priced models often skimp on are: chassis capacity and length, engine size, transmission model, quality of wiring and plumbing, cabinetry construction (type of wood and finish, hardware, etc), flooring and upholstery materials, and sizes of tanks, batteries, etc.
The rest of the choice of a used rig is its present condition. A poorly maintained RV is probably crap even if it was great when new. However, if you are buying a "handyman special" to fix up yourself, buy the the one that was originally better built.
Don't worry about whether the manufacturer is still in business - it's largely irrelevant anyway. The newest rig you are considering is already 8 years old and the manufacturer has long since ceased even the minimal support they gave when new. Most of the chassis components, applainces, and plumbing/electrical stuff will have come from 3rd parties and will still be available or at least replaceable with new stuff.