I’ve done a lot of searching and there aren’t many concrete explanations out there. One that I read is that East coast versions are often lighter (different axles, windows, smaller tanks) than Western editions because they assume people on the east coast are hauling through cities more often and staying in campgrounds. The western units were made for more rugged terrain. They’re usually heavier and geared more toward people who are boondocking more often. How much truth there is to that? I’m not sure. Others claim it just has to do with where the trailer is assembled and transported to. I’m sure that can also vary between manufacturers. I’d love to know if anyone has a better explanation, but this is the best I can come up with