The only type of 12V compressor I would carry for the truck size tires on Class C motorhomes would be the heavy duty ones that serious off-roaders use.
These VIAIR 12V compressors are considered as pretty good and are examples of the type that I would trust to do the job properly. I'd recommend their models that use the heavier input cables that must be clipped right on battery terminals or used with jumper cables. The models that plug into standard 12V receptacles probably would be too slow or get too hot when inflating Class C size tires:
http://www.viaircorp.com/portables.html