Interesting ideas from Raul, many of which I like. Certainly the difficulty of comparing arms is not easily overcome, and great care must be taken when making or offering comparisons. Synergy with other components - especially cartridges - makes a huge difference. Of course if you hear a tonearm with five different cartridges and you like (or dislike) every combination, it becomes a reasonable bet to buy (or avoid) that arm.
I don't quite agree that a tonearm design has to be "complete" before it becomes desirable to purchase. That almost implies that if a designer discovers some way improve his arm he shouldn't introduce it. I doubt that's what Raul meant because it's absurd. Cartridges, preamps, amps and speakers are improved all the time. So are automobiles and golf clubs. Why not tonearms?
FWIW, some of Raul's examples are actually counter-examples. The Rockport arm WAS altered after first being introduced, to improve its bass response. The SME IV is available up to version IV.vi. Should we now strike those from the list of acceptable arms just because the original version has been enhanced?
Many of Raul's other examples haven't been improved for the simple reason that no one is making them any more. You want a newly made Brinkman, Audiocraft, Rockport, Micro Seiki, SAEC, Dynavector, Ikeda, Satin or Technics? Sorry. No such thing. Would those designs have continued to evolve if the arms had remained in production? Nobody knows, but there's no reason to think otherwise. None of these arms is perfect, right? It's certainly reasonable to believe the designer would have continued to improve them if he'd had the opportunity.
Raul's beloved Moerch DP-6 (a fine arm by all accounts) has at least two obvious weaknesses: it has breaks in the wire and its VTA adjustment is rudimentary. No one would argue that either of those is desirable, they are compromises at best. If the designer fixed one or both of these shortcomings tomorrow and renamed the arm DP-6 MkII, would Moerch's top arm suddenly become less desirable? Of course not, just the opposite.
Yes, a design should be well thought out before being brought to market. No doubt some designs haven't been, Raul would know better than me. But an improvement every few years after careful testing seems like progress. Herb Papier introduced the TriPlanar MkI in 1967. We're now up to MkVII, so there have been six upgrades in 38 years. One upgrade every 6.33 years seems reasonable for a component with as complex a job as a tonearm.
