Agree with above. Load it as if for a trip, weigh it, set the tire pressures accordingly. See how it drives. I think you'll be pleased.
Then why do so many of us have Fords?
1. Ford's been more consistent in offering Class C chassis, while GM was on and off, 1-1/2-ton (E450/4500) on and off, Workhorse on and off.
2. This doesn't affect you with the size coach you're buying, but the current 4500 doesn't allow the amount of frame stretch that E450 does.
3. For a lot of years, Ford offered a better transmission. At the moment, GM seems to have caught up.
Personally, I like GM stuff, and I think the setup you're getting should be very nice. The engine being slightly smaller than Ford wouldn't bother me.
As I said, I think you'll be pleased.