Well, like already said, for 2011 or newer, your only choice for Chassis is Ford (F53), assuming you want gas.
As to the question of smaller or larger tires: Yes, some larger Class A gassers have the big 22" tires, while some will have the smaller 19.5" tires. As to pros and cons:
22" tires will ride better, and be a little less 'squishy'. That, and they typically will have a little more weight allowance.
However, the disadvantage to the larger tires is that they are a good bit more expensive when it comes time to replace them. Also, if you are one that choses to carry a spare tire and wants to be able to change it yourself...Unless you're in really good shape (body builder almost), this is MUCH more difficult, almost impossible, with 22" tires. Much, much easier to do with 19.5" tires. If you are one that maintains your tire pressures yourself, doing so with the 22" tires can be a bit more expensive, due to the fact they require more PSI, hence (possibly) a bigger air compressor.
Anyway, hope this answers your question.