Either one would be okay, but it may be pretty slow and none to comfortable going.
I do agree that an air suspension will be smoother riding. If the road has any sudden changes in slope, you would be wise to check the ground clearance and approach and departure angles of whatever units you look at. Some motorhomes are fairly poor in that regard, and some others are worse.
Edit: I should add that the chances of finding a full air suspension in a 30' motorhome are on the slim side. They mainly are used on diesel pushers, and those are typically longer because of weight and balance issues (associated with fitting the engine and transmission behind the rear axle).