I'm not sure about all the differences between the two mixers but one
thing to look at is how the bowl is held by the mixer. In my mixer
which is a KA smaller one, the bown is held by a sort of screw in
fixture on the bottom. My mom's KA which is larger and circa 1975 has
two arms that come out around the bowl and hold it in. I think the
older model is superior as with tough dough sometimes my KA bowl pops
out of the fixture.

Good luck.