Up until the past 4/5 years , Class A built on Ford chassis used the 19.5" and Workhorse used the 22.5". Then Ford also switched to the larger size when they started building chassis with higher GVWRs,
JMHO: The larger tires make for a more stable platform and a more comfortable driving experience.
Caution , always find the coaches weight sticker and look for the rated CCC. ( Cargo Carrying Capacity ) many older class A coaches , although they have large spaces to carry items, some don't have the capability to handle the weight.
B-in L's 2005 , 35' Tiffin on a Workhorse 22,000lb chassis was always loaded to the max and handled poorly because of it.
Again , JMHO, in the length range you're looking at, the coach should have a CCC. of 2500 lbs. minimum; B-in-L's was only 1,400.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.