Fast forward to the 21st century. Fiat has the worst build quality this side of a Yugo. They will soon stop selling them here in the US I suspect. Dodge and Jeep are also bottom dwellers. Ford is right at the top. Ford took a hit for a a few years from the issues with the Microsoft infotainment debacle, but seem to have gotten over that.My 1974 Fiat 128 was bulletproof. Not literally, but figuratively. It would not die. Unless it burned up too much oil and the engine would stop, but I'd add a quart and start it up and take off. Try running your Transit without oil until the motor stops and see what happens. It would be an interesting experiment, and a great story to share.
But really, as mentioned above, different specs and sizes and construction for different requirements. I don't know where the "DucatoMaster is cheaper" came from, when I was ready to buy the ProRam was actually MORE than a similar Transit. They started out cheaper, but something happened.