Either rig should have at least 3,000# of payload which is fine for a 25' C. Check the door sticker for exact numbers. The Ford is an E-350 with the 6.8L V-10 mated to the superb 5 speed Torque Shift transmission. The Chevy will probably be the 6.0L V-8. Both are excellent and plenty of power for a coach that size.
Check the fuel tankage available. Many coaches that size only come with 40 gallons and the optional 55 gallon tank is what you really want/need. Mileage will be about the same, perhaps a tad bit better with the smaller Chevy V-8.
The chevy cab will have a little bit more legroom and overall the Chevy will be about 6" longer than the Ford. Ford offers an excellent power drivers seat that is worth having.
For what it is worth there are far more Fords out there but service for either should be readily available just about anywhere you travel. Both should be rated to tow up to 5,000# though a toad weighing much less is the way to go.
We have had a 2012 Nexus Phantom 23P on a 2011 E-350 chassis (which is 24'6"), for 2 years and 23,000+ miles and could not be happier with the ride and performance. Our payload is 3,363# and we have yet to use more than about 60% of the available storage. Mileage consistently averages 9.5 (at 55 - 63 mph), and that includes some generator time.
:C