I've had a Dutchmen (before Keystone bought them out). I've had a Keystone Springdale, a Keystone Outback, and now a Keystone Montana High Country fifth wheel.
As far as which one was the best, it had to be the Dutchmen and the Springdale (before Keystone bought Dutchmen out). All my trailers were purchased new.
I think the biggest difference between the first 2 and the second 2 is the fact, my first 2 did not have slides and were shorter. Another factor, even though they all were purchased new, they were still old school build. Granted, RV build has been in the toilet for the last 30 years. But things really went down hill around 2010, and Covid caused RV build to absolutely tank.
If you look at the manufacturer's web sites, you will find, that the models are put into 3 different groups. The starter campers, the mid-range campers, and their brand high end. But the fact is, they are all built out of the same plant!
Electronics has become the all important factor in campers over the last 7 or 8 years. Where manufacturers have failed to maintain a quality build, they have installed electronics to razzle and dazzle and an excuse to increase the bottom dollar. So, build quality has gone down the toilet, and campers are now installed with electronics that seem to be more problematic than successful. Still, it's the "glitz" of the new camper that catches the eye of so many not the actual functionality of the camper itself.
I been reading and participating in RV forums for the last 25 years. I find it interesting that someone who complains about the location of the black tank discharge pipe and the position of the slide valve handle is called out as horrible build quality, "what were they thinking?" And someone else will call out the front cap is delaminating and ask the same question, "what were they thining?"
And then, there are those who really do simply abuse their campers. Think of it this way. A little girls play chair that she'd sit on in her little play house is designed for the weight of a little girl that weighs less than 50 pounds. The chair supports that girl just find. That is good quality. It's done what it was designed to do.
Now along come dad who weighs 300 pounds and decides to join the little girl for make-believe tea and sit on that same chair. The chair completely collapses. Does that make the chair a "bad quality" chair? No, it wasn't designed for that purpose. It failed because the chair was not used for it's intended purpose.
The same is true for so many owners of RV. The purchase a "starter" RV with the idea they can take it off road, down wilderness paths, across scorching desert sands. Or they can use it in the dead of winter, or in the scorching 120 degree temperatures of some Western state deserts. Then they ignore any maintenance, repairs, and then complain ... where's the quality?
The quality is in the owner of the RV. None are above repair and constant vigilant, ongoing, never - never ending repairs and fixes. None!
If they are used for their intended purpose and constant vigilant upkeep is maintained, then ALL of the are good quality.
Starter campers are designed for the 2 week vacation schedule folks who might take of an occasional week-end or two also.
The mid-range are those who want to extend a bit into a little colder weather and a little hotter weather (usually 2 air conditioners is the indicator here.)
The high end version is designed for the longer timer and some as 4 season. Yes, they can be used 4 seasons, but they still require a LOT, and I am not joking ... a LOT of prep work and attention to be able to be used in the instream weather conditions. But not necessarily designed for off-roading.
Anyway, "quality" is in the eye of the owner. They are all good, if used for the purpose they were intend for.