Our very first motorhome is our Tiffin. We have had our share of issues but mostly related to its age. Quite simply, we liked the floorplan and accessories better over any of the Newmars in the same price range.
Tiffin is currently working on the roof rails - warranty item. Since we are second owners, this is great. We have found their factory service to be outstanding compared to the brands of fifth wheels we owned in the past..
In our case, the decision really was based on lifestyle and the Tiffin fit ours.
The items which have been issues have not been Tiffin's problems. Frig, exhaust manifold, throttle sensor...Those kinds of tings can happen in any older rig. Luckily, we also purchased an extended warranty specifically because we've never owned a DP before and were a bit concerned about the cost related to those repairs.
However, we purchased from a dealer. Wouldn't do that again. There are many used rigs which have been lovingly maintained by their owners out there. We would find one of those..