Technics SL-1200GAE or VPI HW-40 or …?

As regards the idea that a mat should be of the same durometer (hardness) as an LP, one ought to keep in mind that that strategy is a two way street. Rumble or any other noise that can emanate from the bearing or motor can be transmitted into the LP by the same route. So, if you adopt the principle that the mat ought to transmit energy into the platter (I don't disagree), you then have to worry about isolating the bearing and any other sources of noise, like even that which can be transmitted by the belt from the outboard motor pulley of a BD, from the platter and mat. Denon paid some attention to this issue in their higher end DD turntables, back in the 80s.

A familiar Audiogon motif: OP asks should I buy A or B. Responders say buy C instead. I would only say to disregard a reviewer who says there’s no difference between the Technics and the Stealth. Sorry I can’t help with your choice as I’ve not heard either TT. I advise you to take a careful look at the features of both as regards tonearm and TA mounting, platter construction, ability to dissipate extraneous energy, etc., and use those factors in your decision making. Their both going to keep near perfect speed stability.