If I'm not mistaken, Mec-Gar still makes the original manufacturer's mags for all Beretta pistols, so there's no difference at all between them and they should be equal in every way!
+1Mec-Gar is not the OEM manufacturer of basic Beretta magazines for the duty size guns, both PB in Italy and BUSA are. The simple test/proof of this is that Mec-Gar does not make PX4 magazines and they are not available through them. BUSA makes the magazines for the .32ACP Tomcat too.
MDS= Meccanica Del Sarca, is a wholly owned Beretta subsidiary which also makes Beretta duty sized pistol compatible magazines with different roll markings.
Mec-Gar once made the OEM magazines for Beretta's smaller caliber pistol lines (84, 21, 950,) and still makes after market magazines and specialty OEM "anti-friction" magazines for the M9/92FS.
Between their own capabilities and those of MDS, they do not need Mec-Gar as the OEM.