I have only owned two trailers, a KZ Spree for six years and now a new Jayco Jay Flight.
As far as initial build quality I would rate the KZ an 8 with minor cosmetic issues holding it back from a perfect 10. During the six years (7,800 miles) I owned the KZ I had one plumbing issue (shower drain became detached from the shower allowing water into the belly of the trailer), a short in the running lights (wire rubbing against a sheet metal screw resulted in a short and blown fuse), a speaker that stopped working and intermittent functioning of the furnace start-up function. All were fixed under warranty except the furnace issue went away on it's own.
I haven't owned the Jayco long enough to comment on reliability but fit and finish I would also give an 8. There are minor cosmetic things that you notice once you've spent some time in the trailer. So far all the system are working (short three day/two night camping trip) and time will tell if long term reliability is acceptable. I've heard from people that have owned them for years and never had any issues while others have had issues right from the start (should have been caught during the PDI but that's another conversation).
While the manufacturer is important as important is the thoroughness of the dealers inspection prior to delivering the unit to the customer. I hear of so many issues that are really the result of a poor inspection by the dealer, things that should have been caught and the customer have never seen.