My best advice when shopping this broadly is to visit a larger dealer and poke your head and fingers into where you can't see or it's hard to see. IE cabinet corners or around edges. You can tell a lot about a company that cares (or doesn't) about quality when you look at things most people don't. IE rough edges, shoddy or sloppy plumbing, loose wires instead of tied down and clamped into nice straight lines. Open and close cabinet doors, solid wood or flimsy pressboard? Do the doors clunk in or feel like you might break something when you shut it?
There is a lot of pretty sizzle in new coaches and if you can see past that, it's pretty easy to tell quality.
Itasca/Winnebago are the same just different colors and ours held up really well.
We were also impressed with Newmar Baystar lines for quality for the $$. Other brands felt cheap. There are other good brands out there but these were the two we narrowed in on when we were shopping. Tiffin at the time was having issues and the units we looked at did not impress me at all quality wise. But then there are a lot of very happy Tiffin owners so I must have seen a bad batch.
If you are looking used then maintenance and use are better indicators over original build quality. Although the better constructed the unit the better it will last.