Those brands may not be terribly different in that they 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 as examples. But even here, you will find some folks who have had experiences outside the wider experiences you hear about.
Choose a floorplan that fits your needs. then set a price point. Keep your tow vehicles limits in mind as well as planning around GVWR not empty weights.
In general manufacturers build basically the same floorplans across several product lines.
Appliances are basically all similar including quality unless you go to the high end units, most brands use lippert products for structural members, and furniture that is built in is usually cheaper than furniture manufacturers products.
For quality and durability, think about the issues you have seen in your current unit.
Particle board is cheaper than plywood, which is cheaper than hardwood. And as those products go up in price so too does durability.
Screwed and glued joints are better than nailed, which is better than stapeled.
Countertops and sinks are another high visibility item plastic sinks and toilets are cheaper than ceramic toilets or stainless steel sinks.
Look for how well everything appears to be assembeled, unglued trim, brads sticking out or stapeled engineered wood products are items you likely will be repairing in the near future. Expect to do much of this yourself, dealers tend to keep units for weeks for items which should only need a couple hours.
And dont believe that since you are moving every six months that buying from a big chain is better for service, most locations are so backed up they are near impossible to get prompt service, better to have a brand that independents can assist you on.
The last six months you should have learned a lot of what to look for, dont fall for shiny baubels, look for a more solid base.
Good Luck.