Which one to get.

Welcome!

There is really no way to answer your question with any accuracy. First and foremost you need to drive as many examples of the cars your considering to determine first which era you actually like driving. The SY series cars are mechanically simpler (note, that's not simple), and the SZs started out almost the same (though that's when fuel injection came into play for almost all markets) and got progressively more complex/electronic/computer controlled throughout their production. The addition of active ride suspension and ABS as the SZ era progressed also added levels of complexity related to both.

Late 80's spirit with CIS fuel injection. You won't need to worry too much about miles, lathes or English wheels as the car was designed with an etch a sketch

For greatest durability, probably, Spirit/Spur '87 1/2-'89 (chassis number 20,xxx). Mid to late of that series added ABS to the injection. That said, your appreciation of one style and handling/ride is highly subjective. Driving a bunch before you buy is excellent advice.

'89 Turbo R

Silver Cloud/Bentley S, or older.
You will get more use from your lathe on these cars.
The Shadow/Bentley T is pretty complex, and then after that you get into all these problematic circuit boards.