Actually,
IEIs -> the most nice, but also potentially the most nasty. Definitely have difficulty with the "sanity" thing.
LSIs -> can be a bit cold and distant (and not outwardly "nice" as a consequence), but typically not ever nasty.
EDIT
This is my Alpha P.O.V. I see my SLE dad and IEI flatmate as being bitchy/nasty/overly critical (as spurts when they're not being nice), perhaps because they aren't avoidant of "bad Fe" like Alpha Irrationals like me.