Function, flexibility.
Steve at VAS used to work with VPI, and is a big fan of Uni-Pivot arms. He has more respect for the father than current production, true?
In any case, he has multiple arm wands adjacent to his table, with multiple cartridges, including MONO of course, and if you are close enough to pick up a cartridge from him, he demo’s it on his VPI.
Metal/3D/newer anti-resonance ... If you do not hear anything wrong, why chase ’improved’?, I would not buy a new tonearm, but would add an arm wand or two, and a few cartridges, one Mono of course! Steve built my mono cartridge for me,
I use removable headshells on one arm, fixed stereo on one arm, fixed mono on one arm.
You will certainly hear the differences of cartridges, I cannot hear tonearm wire differences. I doubt you will hear any 'anti-resonance improvements UNLESS you have an existing problem, I'm certain I couldn't.