Rank choice of three turntables

I did not replace the entire plinth. I reinforced the plinth with slabs of aluminum which I bolted to the bottom, adding mass and constrained layer damping. I did replace the arm board.  It felt light and insubstantial to me where I was trying to maximize mass and stiffness.  But you are probably correct, and I was wrong, to imply that it is made of MDF, if you can detect that it is truly a multi-layer sandwich of some sort of solid wood. My error. I did not throw the arm board away; I still have it. It was used as a template for making the aluminum arm board that replaced it. I further reinforced the alu arm board by bolting to it another slab of alu which is mounted down below the opening that houses the armboard.  That lower level alu is also coupled to the bearing, or as close to the bearing well as I could arrange. This setup is specifically for my Fidelity Research FR64S tonearm with B60 base. On the FR64S I have my Koetsu Urushi in an 18g Ortofon LH9000 headshell.  All this mass is good for the tonearm and cartridge and also probably reduces any TT resonances. 

Cast iron, or any iron in the platter material, is not always compatible with especially LOMC cartridges that have powerful magnets.  I think this issue has been cited by TD124 users. Caveat emptor.

Eno, I have not had a problem with discoloration of the platter of my TT101, but if I did, I would approach it as if it were a piece of discolored metal, in terms of how to remove the undesired stain. But there are limits to what you can do to a TT platter that must remain balanced or as near balanced as the factory tolerated. For example, I would not try to grind on the metal or polish it too extensively with power tools. Gentle is the way to go. I would find a way to live with it if gentle methods were ineffective.  The only part of the platter that shows when it is under a mat is the polished edge. Is that where you see discoloration?  Best thing I did for my TT101 was to enhance the mass and rigidity of the plinth by adding aluminum pieces below the deck and replacing the MDF arm board entirely with a piece of solid machined alu. I further re-inforced the arm board from below with more alu that couples to the bearing.

If the TT101 is working, it’s my favorite of those 3. I own one, and I have owned two different SP 10 mk2. The MS will have some admirers too; I’ve no direct experience, but I don’t care for the tonearm mount design. I doubt anyone here has hands on experience with all 3.