Bpoletti, I haven't tried the OC9 ML II or III but I have compared the AT33 PTG-II to my retipped 103R. The comparison was done with two separate wands on my Phantom arm and current setup.
While the AT33 sounded competent enough, it didn't present music with the dimension and involvement of the Denon. I also thought it was less transparent - certainly less realism to the reproduction (for me).
Mechanically the cartridges are quite different, the AT cartridges are lighter and have higher compliance. It's possible they may suit a lighter arm or different setup better.
