Regarding chassis: I've been very pleased with the Freightliner chassis. Freightliner provides a free help desk 24/7 that is very helpful when you're trying to solve a problem.
I've never owned a spartan or roadmaster chassis.
Be aware of the trailing arm problem that affected some chassis made by Monaco. There is some info about that problem in the link below:
trailing arm info Probably most of the rv's with this problem have been repaired, but worth checking.
Try to drive several different motorhomes, paying attention to handling when encountering crosswinds or buffeting from a passing 18 wheeler. You will find major differences.
Good luck with your search.
Fred