Are linear tracking arms better than pivoted arms?

Dgarretson you are right - a very short linear tonearm (like Souther or Versa Dynamics) can indeed feature very little horizontal effective mass.
But much more important it features a very small (= short) lever.
As said earlier - the very short linear tonearms do not show the big problem with the long lever and subsequently the huge lateral force applied by this lever to promote progression.
THese short linear trackers (and this was recognized by their designers) do have problems with not only warped records, but with every little tiny height difference in record surface (and there usually are hundreds of tiny valleys and hills for your stylus while tracking a record groove).
The problem here is, that the vertical lever is very short too and thus every little tiny height difference on the record is huge for the cantilever and stylus. Huge VTA/SRA changes in a long row - up and down the groove highway over the many lovely hills and valleys of the lake district in the midlands of Britain.....

Seriously - as Mentioned before - the problems of the linear trackers are all mechanical issues of the most basic mechanical laws and models.
It is not about friction - it is about long and short levers and the point that the stylus commands the progression.
These problems can all be solved. No doubt about that. "We, the people..." long have all needed electronic and mechanical tools at hand to design and produce a linear tracking tonearm allowing any cartridge to track at zero error line without applying any lateral force on the cantilever at any time.
A linear tracker with groove margin compliant progression independent from any derivation of the cartridge/stylus/armwand.
It is not a big deal, but it has not been done yet.
That was all I am saying so far.
I certainly do not want to tease any owner of linear tonearms. I too did own most major linear tonearms too.
Each of them had its promises and was tempting in one or two sonic details. But none so far did address all the issues in linear tonearm design.
It is not about any heroic design attempt either - there are no heroes in audio, thus we won't see any heroic design.
After all, a hero is someone overcoming his/her fear, fighting the battle, eventually surviving and maybe finds someone who remembers and tells the story.
The physical model of linear tracking tonearm with its force vectors is there. It is no secret.
But just because there are some linear trackers out there since the early 1960ies, doesn't mean that the concept has already been brought to its promises.

"The problem here is, that the vertical lever is very short too and thus every little tiny height difference on the record is huge for the cantilever and stylus. Huge VTA/SRA changes in a long row"
Thank you, this is very clear. Now assuming a record that looks nominally flat and is clamped or vacuum attached, are there some numbers that can be plugged in to this problem so information concerning choice of cartridges for specific designs can got from manufacturers?
In simply looking at my Souther track, it appears to snake along so that it's tracking error is constantly changing. The shorter the arm the worse this is. Do air bearing arms do any better?

Samujohn, the problem of the short vertical lever is independent of the bearing principle. Even a (purely theoretical of course...) very short pivot tonearm would face the very same problem. This has nothing to do with friction or bearing type.
Problem is, that most do assume, that a record is flat. It is anything but that. Even the very best possible pressings out there (King or JVC/Japan) are a nice landscape with countless hills and valleys under a microscope.
Thats why very long tonearms do provide - independent of cartridge or mass - kind of more stable sonic picture with more inner peace. They have less change in VTA/SRA.

Fascinating thread for me, as I just acquired a Souther SLA-3 the other day.
There has been some hot-tempered debate, some baseless opinion and some pseudo-science; all the elements needed for a real honest-to-goodness internet forum!
There has also been all the elements of a reasoned discussion for which I thank those of you involved on that end.
I look forward to the challenge of getting the best sound I can out my new linear tracker, I'll be experimenting with cartridges of differing compliance as well as differing counter-balance weight placement, etc.
I am thankful there is a marketplace like Audiogon where I will be able to purchase used carts at a big discount over new.
I am thankful Audiogon has this forum where perhaps with your help I will be able to maximize the pleasure I get out of my new arm.
And I'm thankful that if I despair of reaching cloud 10 and can't live on cloud 9, that one of you will purchase my Souther and carry on!

My understanding is that some stylus shapes are more VTA tolerant than others. This information should be available from the manufacturers, so one can see what range of VTA tolerance is needed by each arm. In any case, the records vary so much in thickness and in cutting angle that precision in that area is almost useless, unless one has a quick VTA adjustment and a notation on every record jacket. I really miss that feature which I had with my old MMT arm. Unhappily, despite that feature, it never really sounded all that good.