I can't speak for rust issues, but from what I witnessed the Mercedes/Dodge/Sprinter abomination thingies are absolute garbage. No matter where they are used. Some people say the newer ones are better. But that's cuz they're still new. Yes. It seems everybody is using them. But once upon a time it seemed everybody smoked cigarettes, too.
From what I saw, the Econoline was a very solid unit. There were about 25 of them at a delivery company I once worked at. And although I wasn't a 'real' mechanic, I very often assisted the mechanic with maintenance and repairs. I had one with well over 200k on a horrific rural route for 2 years and thrashed the bejeezus out of it quite a bit. The 4.9 I6 was a fantastic engine. The later Essex V6 was good also. But on some of them, sometimes the intake manifold would crack. No big whoop, really. Typically R&R once and it never happened again.