IMHO: An E-450 on a 24' {or smaller} Class C is overkill. You will get a stiffer ride, worse mileage with less available power. Both have the same engine/drive train but depending on what years you are comparing the 450 will be 2 to 3,000# heavier and that is for every mile you drive.
{The 450 has a 4:56 rear end vs the 4:10 on the 350.}
My 2011 E-350 has a GVWR of 11,500 - Ford upped that to 12,500 on the 2012 chassis with virtually no changes {go figure?}. Compare that with the 450 which has a GVWR of 14,500. If you are going to tow heavy or really like to load up your rig then the 450 becomes the better choice but most folks simply do not need that much payload in a 24' C much less an even smaller model.
Even when towing my 6 X 10' {14' overall} cargo trailer with an 860# Indian motorcycle {bike and trailer weigh 2,220#} and the coach fully loaded we are just under our GVWR and the ride and handling are outstanding, smooth as a babies backside and passing trucks, even on a windy day are barely noticeable.
Since I have no need/can't use, any more payload the smoother ride and better mileage of my E-350 continue to work well for us {this opinion is only based upon nearly 6 years and 50K miles from coast to coast and then some}.
As always... Opinions and YMMV.
:C
