The bonding/anti-bonding of the MOs - gives the amount of pi bonds in the molecule (just atom-and-atom bonds; not "pi conjugated system"):
a filled bonding MO suggest one more pi bond a filled anti-bonding MO suggest one less pi bond The Aromaticity - all about the stability and reactive electrons:
anti-aromaticity: has lone e-'s. They are likely to escape/grab e-'s from other molecules (a.k.a. "reactive"), thus making it very hard for this molecule to stay itself (a.k.a. "unstable").
aromaticity: has no lone e-'s. Every pi e- are paired in the MOs ,leaving no e-'s wandering about and causing troubles. It's not likely that this molecule change its structure, thus it has a high stability.