All the V6 diesels are Sprinters, 2007 on up called the NCV3 chassis. The NCV3 is a vast improvement over the T1N 2002-2006 Sprinter, especially in construction and rust prevention, (however the NCV3 has way more engine emission related issues).
The "cheap" construction as you call it is because of the weight restrictions the Sprinter chassis has to have. 11030lb GVW maximum with the NCV3 chassis, even less with the T1N.
In my RVing experience over the last 30+ years, Fleetwood is nowhere near the quality construction that the Winnies are.
Bob & Sharon
Eastern Kansas
2013 Winnebago ERA 70A
Class B Van