OP
My system and speakers are very revealing, but I don’t hear differences between each different TT or Tonearm once setup properly. At 76 years old, I can still hear differences in cartridges, thus the TT/Tonearm is out of the way enough, doing things right, that’s all I want. Ease of tonearm/cartridge change/setup is important. Perfect speed, immediately and forever please. Accept and hold adjustments please.
My choices, including QLDD for TT, are based on solving/avoiding problems, sensible science, features, for myself and others. Like others here, that path has been partially steered by gifts and inheritance, as well as luck, great buys, friends and random acquaintances, and my ’hands-on mr. fixit’ personality. I am a retired Interior Designer, I specialized in Corporate Office Space, so appearance is important.
I have experience hearing speed variations. Both my prior Thorens TD124 Idler Wheel and current Mitsubishi LT-5V Belt Drive TT in my office require adjustments to speed: let them warm up, adjust, play, check every once and a while, the room temperature might affect the speed. QLDD, on/play all day and night/off.
Sensible science: I believe in the science of a longer arm, which is why I was drawn to my Blackbird which is 12.5" effective, however I would not say I hear a difference, I would prefer it had the features of the Mitsubishi 505L, in fact I may buy one, my right side arm-board can be rotated 180 degrees, I can resurrect the 270mm hole in it (from a Victor 7082 arm, that has a 45 adapter in in now). Both arms are 270/282mm 11-1/8" effective.
I have a second AT160ml on the way here, after I compare it to the one I just got one will go in the 12.5" long arm, other in the 9" acos lustre, and I'll get some younger ears over here.