How do you choose a turntable ?

There seems to be a "push" to have exotic materials, small batch runs, "anniversary" models, that really do not make the TT better - just more unique. Are the newer latest editions leaps forward compared to the previous model....often = not. Try an intro TT you can "play/learn" with. In my own experience I would not buy a used TT, unless it comes from an audio dealer that will back the purchase for at least a year. Used phono stage = yes, but not the TT. 
       There are different models/lines that have two paths...one for those that like to tinker (a lot) & one that is just set up once and play with minor tweaks...then you get into unpivot or gimbal, straight tonearms and S arms, direct drive vs belt drive, style/design = minimalist vs traditional look vs modern.  To complicate things - matching a synergistic phono stage with your TT & your cartridge choice can be an experience in itself. The cost of vinyl albums has also increased significantly in the last 10 yrs.
       If I was doing it over again and wanted a starter TT....look at the entry line of VPI (more traditional look) or Rega (more minimalistic). VPI makes an entry model = "the Forever Model One", great rock solid system with a ten year warranty, but a little pricey for a starter ($5500). https://www.stereophile.com/content/vpi-forever-model-one-record-player
A even more affordable and great TT at the price point of under $2000 for a starter system = Rega Planar 3 RS Edition. https://www.whathifi.com/reviews/rega-planar-3-rs-edition 
If I was going to go all in and not worry about upgrading... get a one & done, then the Technics SL-1000RE-S Reference Turntable with tonearm would do well: https://hifiplus.com/articles/technics-sl-1000r-turntable/
      I am an advocate of Soundsmith cartridges....great company that make really good cartridges...their rebuild offer for a minimalistic price can not be beat. And when you note that each album you play is about a 1/3 mile of stylus wear per album - you get about 2000 hrs +/- before needing a whole new cartridge or doing a rebuild. I just got my rebuild back from them…exceptional company. 

We probably never end up with the best turntable we can afford, but we can convince ourselves that we do.

OP, ..."ghdprentice, you approach it as a scientist or/and an engineer." 

Guilty as charged. I am trained as a scientist and worked as one for a decade and worked as an engineer for a while. So I approach things methodically. 

Depends on what level of turntable you are purchasing. Nuances/subtleties are magnified on a higher resolving system. Turntables all have a house sound. Clearaudio, Rega and VPI will all sound different with the same implemented components.

" Everything should be as simple as possible, but not simpler." Albert Einstein.

Turntable is a seemingly simple thing, it's not tape deck. That's the advantage of it. Well designed and made table can last for decades with minimal care. Might have to replace a motor. Decks can and do last for decades as well, not with minimal care, though.