Dear Johnp,
First of all, thank you so much for taking the time and energy to type out your report and post it here. It seems you took great pains to get valid data relevant to a comparison of these great turntables. But I must confess, there is so much information in your post that one essential element eludes me; were the MkII and the Mk III BOTH mounted in Steve Dobbins' plinths? Also, what platter mats did you use on the Technics tables? One conclusion that I have come to is that the stock rubber mats, supplied with the Technics tables and with my Denon DP80, and with most of the classic vintage Japanese tt's, are suboptimal at best. I found that an SAEC SS-300 metal mat makes both the DP80 and the Mk2A sound much better.
Also, in some respects your report is at odds with what others have told me, mostly in private, which is that the Mk III is better than the Mk II, as one might expect, but that the differences are subtle and of degree rather than of quality. For example, the Mk III was said by one person to have better bass reproduction, period. Another user who owned both tables told me not to bother with a MkIII if I have a MkII, because the upgrade was so subtle. I have also read and heard that the Mk II had a "dry" sound, as you suggest, but I never read a similar comment about a Garrard 301, with or without Steve's platter. The 301 is generally said to sound full and lush, as you say of your Dobbins-modified version. In an unsophisticated solid slate plinth and using the SS300 mat, my Mk2A definitely does not sound dry, but I can tell where that criticism comes from based on previous listening to a totally stock SL1000. None of this is to say that you are "wrong" in any way. It's just to point out how we each may experience the same thing in a different way. The fact that your panel of listeners reached a consensus is very convincing and makes me think my own judgements may be in error or that this is also dependent upon downstream components. Anyway, I now own a Mk III, so I will soon be able to listen for myself. (BTW, if anyone knows how to access the bearing of a Mk III so as to check and replenish the lubricant, please let me know here or in private.)