What tpi said!!
ron.dittmer's great post should be a sticky!
The only significant criteria for running gear/power train are wheelbase relative to total length, and the quality of the extension of the chassis.
Most manufacturers make the "house" part in 3 qualities: weekend or short camping trip use; extended use; and full time use. Prices vary accordingly. A very few only make high end: coach house, born free, lazy daze. No matter which quality/use level you choose, if used that way the house will wear out long before the vehicle part.
Beware of the "short" class A's. Most are on van running gear, not F53. Vehicle maintainability was not a consideration. I seriously question long term viabliity. However, some shorter true class A's are now available (My first class A was a large - at the time - 23 foot.) I've seen some good under 30 foot choices. Some drivers, or their co-pilot are uncomfortable sitting "out in the open" and in front of the front wheels. For those a class C would be a better choice.
The cockpit of a class C is more survivable than most Class A's in the event of a serious crash. However, Motor Home drivers are probably the most conservative and safe drivers and serious crashes are really rare. If you tangle with a garbage, dump, or semi truck A or C makes little difference.
The most important choice is the compatibility of the floor plan with your use.