Turntable Mats: Rubber, Felt or Cork.

The TTW mat had some sort of massy metal base with a delrin top surface.

Delrin if you’re obsessed with matching to vinyl.  TTW used to make them. Colby Lamb can make them. And if you read other posts, what could match the hardness of a vinyl LP better than another LP? At least two others have mentioned that.

If the OP learns anything here, it ought to be that he has to try a few different types of mat for himself, and then decide for himself which is best.  On the scale of the cost of audio things, that is not such a very expensive experiment to do for oneself.  In one way or another and over a period of years, it is how each of us arrived at our own preferences.

In my opinion, platter mats are like seasoning of very fine food.  Each palate will react differently to one particular choice or another.  And fish requires different seasoning compared to beef stew. Although each of us like to think of ourselves as a searcher for the Absolute Sound, and although most of us believe that such a Holy Grail actually exists, I think in fact we are all prisoners of our own senses and biases.  Therefore, I would make no definitive pronouncement on what is the "best" mat, although I think we can all agree that rubber mats, and maybe also rubbery mats, are not so great (to put it as diplomatically as possible).  Also, within this argument about mats there is a minority who prefer to elevate the LP above the platter (e.g., the much loved Resomat), which is like saying they prefer no mat at all. So this is why I am not blown away that Noromance does not like the Boston Audio mats (whereas I do) or that someone else doesn't like metal mats of any type, or etc.  Likewise, I would have to try Slaw's mat for myself before giving it a thumbs up or down.  I am by the way, blown away by Noromance's ability to give precise numerical rankings in 4 categories for each of about a half dozen mats, especially since in every category, all the mats ranked >5, on a 1 to 10 scale.  So the rankings are really on a 1 to 5 scale.  Seems to me the nature of the platter itself, of the drive system, and of the other elements of the turntable, tonearm, and cartridge are critical co-determinants of the end result.  So Noromance's rankings are only relevant to his turntable, tonearm, and cartridge, not to mention his phono stage/amplifier/speakers/room.

Slaw, you make a good point about the possible coupling effect of a reflex clamp. In one of my systems I use a Sota reflex clamp. I noted that the interface between the bottom surface of the clamp where it contacts the record label is isolated from the record label by some standoffs. I don’t know how effective that is to eliminate coupling of vibration from a motor , But I certainly do not hear a problem. When we talk about vibration from a motor, I guess we are limiting ourselves to direct drive turntables. There really is almost 0 vibration from a good direct drive turntable motor, but there could be bearing noise. I don’t hear that either, with the Sota clamp. This is not to say you are wrong and I am right, it is just my observation. And in general I think coupling of the LP to the mat by using a weight or a clamp has been beneficial for me. I do not go in for superheavy record weights, however.