What defines a good tonearm

I'm in the market for a very good tonearm as an upgrade from an SME 345 (309). Most of the tonearms I have used in the past are fixed bearing except for my Grace 704 unipivot. I dont have a problem with the "wobble" of a unipivot, and they seem the simplest to build, so if they are generally at least as good as a fixed pivot, why wouldnt everyone use a unipivot and put their efforts into developing easier vta, azimuth and vtf adjustments, and better arm materials. Or is there some inherent benefit to fixed pivot that makes them worth the extra effort to design and manufacture
Back when men were men and vacuum tubes ruled, the turntable/arm/cartridge setup separated the audiophiles from the mere consumer/wannabes. The hair shirts among us dared liner trackers and air bearings. Pickering even ventured a magnetically levitated turntable. Now you propose to simplify and rationalize the ultimate spiritual audiophile endeavor. Shame!
Synergy with the turntable is an interesting subject. Would someone care to elaborate?
"Back when men were men" is even more interesting subject but this forum is probably not the appropriate place to discuss it.
But we could discuss 'when women were women' in relation to synergy etc.