Bare in mind that quality in the RV industry usually means heavy. Other than weight, things can still go wrong with the highest end 5th wheels since compared to the auto industry with robotics and quality control to stay competitive, the RV companies seem to be more interested in getting the product out the door as quickly as possible.
However, there are a few top remaining companies out there. Double Tree was a great full time rig. I understand they are no longer in business, but many of their near new units are out there on the lots. Carriage is also a good quality rig. The better built they are of course the more you will pay.