In 1990 J.J.P.Stewart, the author of MOPAC, prepared an extensive comparison of
PM3, AM1 and MNDO. It is published as Vol. 4, No.1, of J. of Computer-aided Mol
ecular Design, ESCOM, Mar. 1990 (a special issue). Hope this is a help.
Pat Plummer, Univ. of Missouri-Columbia