Dear Vernon: I can't say how both cartridges performs on your Yamaha tonearm.
Both cartridges are different designs and one of that diffrenecs on design is that the 90X is a low compliance cartridge against the AC-2 medium one along that the 90X is a medium output against a low output AC-2.
These two different characteristics makes not easy to " rank " on a tonearm and phono stage where I don't have any experience.
I like both cartridges where the AC-2 tonal balance is a little more natural than the one on the 90X where the low bass is somethng to " hear " and a little better than the one in the AC-2: more explosive/emotive.
For the AC-2 " shows " its real quality performance needs an active high gain phono stage ( no step-up transformer in the cartridge signal ), the 90X is more easy to handle due to its higher output level ( no step-up need it. )
I'm sorry I can't be more precise/clear on the subject. Btw, very good looking item your Yamaha.
Regards and enjoy the music.
Raul.
