Had a Chevy based Jayco 23ft Class C on a 2002 3500 chassis with 8.1 Liter engine and Hydromatic (no tow/haul -not the Allison). Now have a Winnebago Aspect 26ft Class B+ on 2006 E450 chassis.
Chevy 3500; Liked the seating position, foot room for driver and passenger, general cab space and ease of getting from front seat to coach area. Did not need any special upgrades to improve handling. Liked the dash layout. Felt brakes were marginal.
Ford E450: Love the v10 with 5sp transmission, very solid feeling, great brakes. Transmission is terrific. Fuel mileage seems to be about the same 8.1 3500 vs V10 E450. Like the air bags on rear axle. The front suspension has some interesting steering characteristics....that is just the way the Ford is. Raised the drivers seat 2 inches and moved it back 1 inch which seems to increase the comfort level in the cab and makes it easier to get from the cab to the chassis area.
They are both good rigs. The 6.0 Chevy should have a mpg advantage over the E450 Ford V10. The Ford E350 mpg will come closer to the 6.0 Chevy because of the higher rear end ratio.
If I had a choice....for rigs 25ft and under I would likely choose the Chevy 3500 chassis with the 6.0. But it all comes down to personal choice as either chassis will work well for most people. Those who really need to haul a lot of stuff or pull heavy loads might want the Ford E450. We have the E450 because that was the only choice offered with the floor plan and design we wanted.
I think the engine and drive train on both units will outlast the coach...the front end of both are probably the weakest link.