Another thing to consider when looking at units is how accessible things are with any slides in. Some designs make it very hard if not impossible to get at certain cabinets, spaces, etc. without putting the slides out--occasionally even things you obviously might want access to while traveling such as the bathroom or fridge.
Also look for the weight sticker, which is often in the back of a cabinet somewhere inside, and consider carefully whether you'll have enough carrying capacity for all the people and their stuff and water, etc. Some class C's in particular are quite poor in this regard; others are better.
If you have any RV shows in the area, it might be worth going one day mainly to rubberneck and see what sorts of things are available. At least around me, the RV shows are composed nearly exclusively of trailers, which isn't quite so useful when shopping for a motorhome, but it can still give some general ideas of useful (and useless) features, etc.
For used RVs, the condition of the particular unit and how well the maintenance has been kept up with and performed is more important than the particular brand, in my opinion. I'd rather have a budget model in great shape than a top of the line one with inadequate maintenance and the resulting (often structural) problems.
A motorhome makes a wonderful way to travel.