the 81 uses a ceramic magnet. Ceramic pickups usually are more compressed, more punchy, have lots of mids (especially high mids), and are higher output (typically, of course).
the 85 uses an alnico magnet. These usually sound more open, have a sharper attack (less compressed), and aren't as high output.
because of the traits of the ceramic pickup, alot of people say its better for distorted sounds, and I definitely agree with that.
Same thing with alnico pickups and clean sounds.
these aren't rules, just generalizations.