If you're using a "real" Amiga you're best off sticking with 3.8.
You lose pretty much nothing as there's not really any software that take advantage of the newer features anyway, not to mention the newer versions have some incompatibilities with mui software, along with adding significant overheads.
And yes, the naming conventions are a bit silly and confusing. Seems somewhat like a petty attempt to make it appear that AmigaOS mui is on par with MorphOS mui.
