We had a 2003 Itasca 24' on a 2002 E-350.
We now have a 2015 Itasca 27' on a 2015 E-450.
We tow a tandem axel 7000 lb trail that we sometimes haul a farm tractor, and other time our car.
The biggest difference I see between the '02 and '15 is the transmission. Because of the different transmissions it's hard to see any difference between the engines.
The '15 has air bags.
Dusty