One turntable with two arms, or two turntables with one each - which would you prefer?

I have a 75mm Thick 'Permali' Densified Wood Board.

I am familiar with Panzerholz produced with 25mm and 32mm Thickness Boards.

The individual from Qualia Lab's who has caarried out the Testing on a large selection of materials chosen as a Structure to be used within HiFi, has made it known on regular exchanges that a 10mm Thickness Panzerholz or Permali are able to deliver the ideal Damping and Dissipation properties for HiFi related purposes, especially in relation to what more commonly selected material are able to offer.

A very good friend used a 25mm P'holz Plinth for many years, and then had been able to source a Thicker 32mm Board.

This allowed for the 25mm Plinth to be compared to a 32mm P'holz Plinth, their assessment was the Bass and Air from a presentation was an improvement when using the 32mm material, the 32mm remains in use today, and I hear this whenever I visit.

Another individual used a 25mm P'holz Plinth naked and another which had a Material called Newplast added, each were able to use the same TT > Tonearm > Cart'.

After a long period of trials, the Newplast was removed, as it was said to have created an overdamped sound which was not as attractive as the Naked Material only.

I have moved away from Mass Material Plinths, as the Perception of being overdamped was noticeable, and not dissimilar to the presence detected when certain designs of a Cabinet Speaker are used. Either of these being detected is an unattractive presence I am not comfortable with, when it is detected during a replay.  

There is only one method to discover if a Densified Wood is suitable to an individual as a Plinth or Sub Plinth, and that is to experience it in use.

Why do we seem to think “hardness” is the most important criterion for a material used to build a plinth? 

lewm,

It's not. Just stating the physical characteristic of Panzerholz. That characteristic produces very clean and crisp parts as oppossed to say plywood or MDF. 

I would imagine that the hardness would contribute to the speed at which mechanical vibration travels throught the material (velocity).

I am not in anyway meaning to denigrate Panzerholz, but the prior discussion centered in many cases on "hardness" not just of Panzerholz but of other materials mentioned. And I wondered why. Seems to me that hardness is concomitant with the necessary characteristics of a good plinth material but is not THE reason why a material is good or bad for a plinth. Yes, a plinth ought to be good at dissipating energy put into it by the turntable chassis. By the same token, granite ought to be good too, but many (not including Pindac) have found it to be less good than other choices. Until now, I did not realize that Pindac had a favorable opinion of granite. For that matter, slate might seem to be a good choice, and it is what I chose back when slate was all the rage and OMA were selling slate plinths for a wide variety of turntables. (Given my contrarian nature, I created my plinths for the DP80, SP10 MK3, and Lenco "from scratch" but using professionals to do it the way I wanted.  When I wrote about my slate adventure on line, OMA were not happy with me.) I am satisfied with the outcome, but I am not going to claim slate (Pennsylvania black variety) is the best choice. Around that time, Albert Porter was selling Panzerholz plinths for SP10s Mk2 and Mk3. I’m sure those are excellent too. It’s interesting to me that Panzerholz is good because it’s made by glue-ing together layers of material. Glue creates a boundary between layers. Energy arriving at the glue line would be partially reflected back and partially transferred across the boundary. I am guessing that because the whole is compressed under very high pressure, that potential issue is ameliorated.  Another choice is concrete; I have used large square pavers from Home Depot as audio shelving.  It works pretty well for that.  Would be hard to conceive of making a plinth of it but fun to try.

I have a table with 2 arms (feikert blackbird, Kuzma 4pt and schick 9,6.  Koetsu Onyx on the Kuzma arm, Ortofon SPU grand royal on the Schick.  I also have a Rega P8 with Hana Umami Red.  Phonostage is Manley steelhead so I can plug all 3 in at once. I really like them all.  If you have the room, I say the more the merrier.  I find a time and place for all of these sounds coming from these setups.  Yes the Kuzma/Koestsu is the best but I still have a lot of fun listening to the others and get a different sound and vibe from them.  I would have more turntables if space was no issue.  I think probably 2 turntables is more fun than one with 2 arms.  Get tables you can add an arm to and maybe you can end up with 4 arms!