I upgraded table and arm in a controlled circumstance-- same room, system and phono cartridge. The difference with the better table/arm set up-- fewer sonic artifacts from the better table/arm combo.
Sometimes, it is hard to discern an artifact until it is gone.
For example, the "halo" of sound that I often associated with record play is simply absent on the bigger, high mass table and linear arm--
The bass is better too, but to fully appreciate that,
I needed to augment the bass reproducing capabilities of my system--
Now in a bigger room, with additional subwoofers.
And the thing that really made a difference was a change of cartridge-- not so much fancier or more expensive, just different voicing. If I had made that cartridge change with a different table/arm and without the bigger room/augmented subwoofers, would it have been as dramatic? I doubt it--but it took more than just a change of cartridge or table to get to this point. The improvements were cumulative. Is that true in every system/circumstance?
I don't know.