Since I'm actually buying Class 'C' number 2, this is what was important to me:
A. Floorplan. If you can't live in it, you're not going to like it.
B. CROWNED Roof. My first motorhome has/had a fiberglass roof. Which is great. But it was FLAT. Which was NOT GREAT. There are plenty of 5th wheels and VERY expensive travel trailers w/ a TPO or rubber roof. I'll take a crowned roof w/ gutters ANY day over a flat one w/ fiberglass. Crowned fiberglass would be perfect. I'm getting a crowned TPO.
C. CCC. Check the cargo capacity. The longer you go, the heavier you go. The more creature comforts you get in it, the heavier you go. Modern day yellow CCC stickers allow for fuel and propane, that's it. People, food, water, etc. all go against CCC. Make sure your rig can carry what you need.
D. Read 'C' one more time, and make sure you fully understand it.