In my opinion either are good a company, pick the floor plan that you like best once you find a contender. As mentioned above there were some problems with some Tiffin models but were repaired by the Tiffin factory as needed.
My brother just traded for a new '14 Tiffin Allegro RED. I was really impressed with the amenities for the price point. The cabinet quality and the floor plan seem nice. He has the floor plan with the sofa across from the large banquet booth.
When we were thinking up grading, I looked at the Tiffin Zephyr and Newmar King Air. Both are nice but we decided to bump it up some more as I wanted a true bus shell.
Good luck on your search. Tiffin and Newmar are still in business and should have any parts available on a used unit if needed.
MM.