9", 10" or 12" tonearms

It is true, the discussion about tonearm length comes back every few weeks and all is said or written about. A good made 9“ Arm is superior to an average 12“ Arm.
Just my personal opinion about it.
A top 10“ or 12“ or longer Arm will give some results which can be interesting for one or the other.
When the customer wants to learn, he has to learn by himself. The typical audiophile is lazy, he looks for someone who „knows“ more than he does and will follow.
Can be ok, but you know the sentence „Ask 5 audiophiles and you will get 6 opinions“?
Best way is to visit other systems and to listen, after a while you will get impressions which will - or can - be a step forward.
Today we have internet and the times are modern, means, in High End - specially in analog - „Products“ came into the „market“ which are made from amateurs, supported from DIY groups, Internet support, Hype, good pricing when writing positive, top margins etc.
I don‘t care about, it is the way it is and everyone can burn his money the way he prefers. Everyone who has to live from „this“ has to defend his opinion and it does not make much sense to support old designs which are no longer available.
But let‘s go back to real life.
A customer can do his own comparisons, he has not to live from it and when the system is good enough to show the differences, he will hear the differences.
I did that, I think, I bought or loaned about 15 Arms and I had (or have) good/average 9“Arms (both expensive), I had 10“ Arm (expensive), same with 12“ Arms and after all those years I think, I do not prefer Arm length, I prefer the brain from the designer, some are better than others. And I prefer science and precision.
It is not a religion, I know some audiophiles who listen with Tables or Arms or Cartridges. I would refuse to listen to any longer than 5 minutes, because it is colored, limited...They are happy with it and don‘t want to know it any better (not everyone is interested in real top performance, a real top review is ok, too)
High End means „High“, not average, not hype(d), it means a better preformance... today and tomorrow we will see the change, average units will become „The Standard“ and when more and more believe in that, it will be „The Standard“.
When you don‘t believe in „The Standard of today“ you‘ll have to work on your own.
Sad, but true.
It is a long journey...

Lets not forget the fact, that the majority of all plinth turntables can NOT accommodate tonearms with an effective length greater than 10" (even the VPI 12.x and Kuzma 4Point tonearms do use a 9-10" mounting distance with off-center bearing location to move around this fact).
Thus any tonearm designer with a remote interest in sales will think twice ( and set aside the whole idea... ) about launching a 12" tonearm.
And it was that way ever since.
Custom audio born tonearms in 12" were always introduced as "off-springs" of their older 9-10" brothers.
All exceptions worth mention were broadcast-clones.
Aside from the points you mentioned - which most circle around less stiffness and increased dynamic moving mass (effective...) - this is one paramount "practical no-go" for 12" tonearms.
But I guess we all can agree, that in terms of geometry the 12" have a natural advantage in terms of tracking arc aspects. The increased mass is no question - well maybe one day we will see the re-rise of low compliance cartridges. Isamu Ikeda just revised his cartridges to lower the compliance......
Yes - in tonearm design it is all about careful choosing and weighting the needed compromises against each other.
The fact that we see many cartridges today with quite heavy body weight but quite high compliance ( certainly NOT a good mixture... it considerably increases the effective mass of ANY pivot tonearm ) doesn't make the game any less demanding ....

All great posts. My simplistic approach: I love the sound of my TT with a Graham Phantom Mkii and contacted my dealer and Bob Graham. Bob and my dealer took care of me and put me in a 10" Phantom Mkii because of clearance issues with my TT - a VPI TNT with Super Platter and Ring Clamp.

Find the equipment that gives you a musical experience you love and the rest will take care of itself.

Russellrcncom,
You might want to also read the posts by Frank Schroeder from 4-29-09: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1235522919&openfrom&51&4&&st100
and his following ones.
These, together with Thom's comments above, should put the matter to rest.
Geometry "advantages," real or perceived are really only one element in this game...
Joel

Indeed - a great thread which will nicely illustrate the inner truth in Syntax' most recent comment here.
Highly recommended to everyone looking for insight into "the game"..