I have a 2014 21QB. it is on the Chevy 4500 Chassis with the 6.0l.
A few things to consider. The Ford may be more likely to have an intergrated brake controller. Check yours before you sign if you need it. Wiring a brake controlled was a huge undertaking because the service information was not available yet, even at the upfitter sites, even on the computer at a GM dealer. PM me if you get in this situation.
If you pick a model that you expect to have a swivel passenger seat, it is not available with the Chevy as shown in the pictures. There are swivel seat bases online, but they require mods for the 2014 Chevy.
My alignment was jacked. It damaged my front tires. GM claims FR needed to adjust at build time. My dealed blames GM, and won't help (they always blame others). If the wheel isn't straight on a straight road, be suspicious.
Some of the Class C Freelanders are available on Ford 350 and Chevy 3500 chassis. They are too close to max weights for me. Personally I'd look for the 450/4500 ones for "21" and up.
My unit had lots and lots of little defects from FR and my dealer has been very little help in fixing them. Almost all of them could have been spotted before delivery. I would check any potential units very carefully, and get the fixes before payment. I'm a month and a half waiting on a fix for a hole in my dinette, as an example.