A good number of threads have been started on which is better-a Shuttle Bus, a Shortie School Bus or a full sized Bus (Or RV, or Greyhound, or whatever).
I started this thread to consolidate the thoughts and hopefully get all the pros and cons in one easy-to-read place.
Here are some of the earlier threads on the topic:
I can't offer an opinion on a full sized school bus-I only know my shuttle bus. For the record, here's what I wrote elsewhere.
My shuttle bus is well crafted. The fiberglass body is bulletproof. I've never had roof leaks, because is it a single piece with no seams. My windows leaked, but after I replaced the flange gaskets (like an hour per window) they've never had a problem, which is not the endless slog I see people going through with school bus windows.
I can easily secure anything inside to the fiberglass body with self-tapping screws. Running wires underneath the bus is a snap because it has a plywood deck that readily receives screws. This makes the conversion work simple.
Engine and drive train are proven systems, solid. I cruise at 65 mph and have no trouble climbing with the bus. Parts are standard, and mostly available at your local auto parts store.
And my seats unbolted in a snap-no grinding. And I could reuse the hardware and the floor and wall tracks to bolt in equipment and fixtures.
A shuttle bus is an excellent option, especially if you don't want to spend the first year of your conversion getting to square zero with your build. And to clarify this statement, I've seen lots of hard work done by others here rebuilding frames, fixing rust and mechanical issues, stripping out seats (particularly difficult if you are not physically strong and determined), all just to get a shell to start working in.