Caravan or motor home? Advice please

Hi, We have just started looking for a touring caravan or motor home. We've been mostly looking at 4 berth caravans with single and twin axles. One of the technical people at a caravan show told us that having a twin axled van can be a problem if wanting to stay at small sites (which we do). Also, it seems there are far more motor homes than caravans on the road. 

What we'd like to know is what are the pros and cons of each? Can anyone offer advice please?

Thanks

Kaz