@teo_audio
If we modified a impact testing rig so the given edge of the moving or rotating platter could impact upon said impact gear, we could probably prove, via data obtained... that idler wheel is better than belt or direct drive.
Not necessarily, the main advantage the old idlers have is the size of their motors and that most of them are AC/hysterisis type motors which self correct if the motor starts to lag. The weakness of most belt drives is their small motors & elastic rubber belt. The problem with DC motors and direct drive is that its like digital - only a little bit out ALL of the time. DC motors have zero torque at a constant speed, only when they change speed does the torque go above zero.
Thats why DC motors need feedback/computators to maintain speed.
Furthermore if you look at the response of AC and DC motors to lag, AC motors recover sinusoidally, whereas DC motors recover trapezoidally. In other words DC motors recovery from speed aberrations is rough compared to AC.
Here is my Final Audio Parthenon with big AC motor, silk thread belt & 26kg platter and record clamp. The motor is controlled by sine & cosine wave generators and driven by a 60wpc Onix Audio OA60 power amplifier. All cabling in the turntable motor drive is phase coherent MIT Oracle.
https://www.youtube.com/watch?v=lwugFlbCOwwVideo playing Carol Kidd ( Linn Record) Dynavector Cartridge, banging the record with knuckle.
Try that with your Linn, Oracle or TW Acustic.
By the way I also have a personally rebuilt/restored Garrard 301 idler ( higher spec than your run of the Artisan Fidelity & Classic Audio 301's ), close but no cigar - cant compete with the string drive Final in speed and precision. The key here is that the silk thread does not stretch.
Oh, forgot to mention the string drive Final was built in the 70’s.