Bring it up with: Bob Graham, Marc Gomez, and the others who conclude that when all of the variables are considered 9" is the best overall solution especially to dynamic performance in the groove. Gomez has degrees in materials science and mechanical engineering. I don't. And you? And I do not and did not say 9" arms are "inherently superior". It's not how I talk or write.
While I am not a mechanical engineer I am an extractive metallurgical engineer who had to deal with processes...in other words, mechanisms with many variables, each having a contribution to the whole. I think you hit the essence of what many people forget to consider and that is, a tonearm is a system. Tracking error is part of the system, resonance is part of the system, mass is part of the system, inertia is part of the system...the list is seemingly endless. To pin a particular tonearm's "superiority" on less tracking error alone is folly because changing length also changes many of the factors listed above. So without data to point to, cause and effect cannot be analyzed which I believe is the case for most of us...all we have are our ears and how we interpret what we hear. I would venture to guess that individuals like Bob Graham and Marc Gomez do have data and in the end when all variables are considered, that is the reason they believe 9" to be superior.
So I guess part of what I am saying is that if we want a particular arm to sound better because we believe tracking error is the end all solution, then said arm *will* sound better. Someone else may believe that white epoxy paint provides a damping effect that an ebony wood arm cannot. And that is all fine so long as we are enjoying how the music is presented to us...
Brock