Hard to assess the last without a floor plan or interior pics, but it seems like families generally gravitate to Class C's for the extra sleeping space typically provided by the overhead bunk, while couples tend to gravitate toward Class A's. Just a generalization, of course.
Our preference is not to have to convert something from day to night use (and back again) each day. I would think in an A with a family, you'd be more likely to need to do that.
As for searching, if you're not partial to a particular brand or model the sources you cited may be best. You can use searchtempest.com to search multiple Craigslist locations at once. If you find a floor plan you love and narrow in on model numbers for the various brands, I found ours on a dealer website by googling for specific make/model.
