I'm an owner of the 5400 ll. I find it extracts more detail than my Nikon 8000 ED, as one might expect, and I prefer to use the KM scanner for all 35mm film.
One major issue in my view, if one has a lot of film that needs archiving, is when to do it seriously and finally? What the 5400 ll produces is a great step up from my first scanner the Nikon LS 2000, just as the 8000 ED was also a lesser step up.
I'm reluctant to keep rescanning the same stuff. Perhaps the 5400 ll is the pinnacle of affordable 35mm film scanners. Tell me it is so.