Well, I am afraid I just can't decide which design is inherently better based on all of your arguments, but I find it very funny there are a lot of fine tonearms of different designs that all succeed in doing a fine job (provided they are matched with compliant cartridges).
Everyone seems to aggree playback is never ideal. You might argue if it's very important to be able to play warped LP's, but I would certainly prefer to flatten them rather than demanding the tonearm to be able to follow the warps. Excentricity is another matter, does one realy enjoy music when so much wow is introduced?
And there is yet another aspect that hasn't been mentioned before. The main job of a tonearm is to keep the cartridge still while it tracks the groove walls. In stereo the signals are cut in 45º angles, with a horizontal and a vertical component. The stylus assembly of course has a very low moving mass compared to the 'fixed' tonearm plus cartridge body, but nevertheless will cause a reaction. Groove modulation may even affect the speed of turntables! So idealy (and only from this point of view) the tonearm mass should be as high as possible, infinetly high to overcome this problem completely. But a very high tonearm mass would obviously introduce a whole lot of other problems... But then again, sound reproduction with records, cartridges, tonearms and a record player is an extremely complicated affair with a whole lot of mechanical subsystems that constantly interact. Everything in designing this gear, including tonearms, is about dealing with contradictory demands and compromising. In fact, almost everything in life is.
And how about tonearm geometry? You may like Baerwadl's, Loefgren's or Stevenson's alignments, fact is on certain rcords one will be better while another will suit other ones better, just depending on where the strongest modulations are.
To return to the original question ,"what defines a good tonearm" may simply boil down to a only one principle. Try and remedy known disadvantages while not introducing or augmenting others. A good design is one that prooves the designer cares. And he would preferably care more for music than for the actual design. I wouldn't argue the value of fine craftmanship, build quality or even looks, but how an arm does it's job is most important. Matching components, a proper set-up and proper maintenance will always help you get the most from any given piece of equipment, regardless of it's design.
So, while it is fascinating to explore the technical aspects involving our hobby, what I find truly amazing is how a crude and necessarily compromised way of reproducing music from a piece of profiled vinyl can be so succesfull in allowing us to truly enjoy the music! I have and have had several fine cartridges and a couple of tonearms. While all of them had specific and distinguishable qualities, most of them succeed in involving music making that makes me forget everything else.
regards, franz
