Dear @mijostyn : " All the best arms of similar mass are going to sound exactly the same as long as cartridge alignment is exactly the same. "
I don't agree with you for two reasons: " are going to sound " and " alignment is exactly the same ".
Aligment " exactly the same "? this is almost impossible that can happens due that always exist tiny very tiny alignment set up deviations. In the other side you posted that best tonearms SOUND de same and latter you posted that tonearm produce no sound and it's common sense to understand that tonearm it self does not produce sound contrary to the cartridge transducer where that electrical signal conversion comes full of MUSIC information, yes the cartridge alone can't sound if does not exist the other transducer at the other end of the system chain but nothing of those is the real issue here.
@larryi @richardbrand @viridian are just spot on.
Two different tonearm with the same EM develops different kind of resonances/distortions that one way or the other contribute to different sound coming from the speakers due that those 2 tonearms are self damped by design and building in different way and even with different " geometry ".
Tonearm it sel fputs a" color "/distortions and the cartridge too due that exist different kind of resonances through the cartridge body, its tracking abilities, its overall design.
mijos everything in a room/system ( including yours ) develops distortions and the owners challenge is to put all those kind of distortions at MINIMUM.
Regards and enjoy the MUSIC NOT DISTORTIONS,
R.