Direct Drive vs. Idler Drive vs. Belt drive


I'd like to know your thoughts on the strengths and weaknesses of each drive system. I can see that direct drive is more in vogue over the last few years but is it superior to the other drive systems? I've had first-hand experiences with two out of the three drive systems but looking to learn more.
scar972
At the risk of disagreeing with those who know more,
- agree with the late legend Tom Fletcher, who thought that powerful motors generated powerful vibration hence audible distortion;
- agree with the air bearing crowd who think that all conventional bearings cause vibration in the platter, which is audible;
- agree with the massive platter crowd who think that moment of inertia is the best defence against vibration whatever the source.

My own DIY all-air bearing TT is capable of demonstrating that inaudible noise emanating from the plastic sleeve bearings of its precision 2W motor, has audible effects on the music. Those effects are similar in character to digital, although obviously much reduced. I note that during the launch of the SP-10R, I was allowed to inspect their motor - and I could HEAR bearing noise when turning the spindle by hand. Obviously that matters.

My DIY TT mounts a modified Trans-Fi linear tracker and a higher end Koetsu. Air bearing is the larger New Way thrust bushing running at 63psi.
For me, direct drive. I use the SL1200MK5 (slightly modded by KAB) 
External power supply. Tonearm trough silicon damper, cardas wiring. I am happy.
My TT drive experience is on the lower end of the audiophile spectrum. After many years of non-vinyl listening, I inherited an old, entry level belt drive Hitachi TT. This table was surprisingly good, but I could tell it had some sonic limitations, especially in the lower frequencies. Probably not because it was a belt drive, but because it had a very mediocre tonearm and plinth. I purchased a Project Debut III, NIB, at a significant discount. I upgraded the horrid metal platter to the optional acrylic one. The table was generally very engaging except for the motor noise between cuts and sometimes audible during quiet passages. I also discovered that I am not as hard core as I used to be and hated having a manual TT. I sold the Project and picked up a  30+ year old Technics SLD-303. It is dead quiet, holds speed incredibly well and shuts off at the end. I think the Project sounded better overall because of it's better tonearm and modern plinth, but not because it's belt drive system. I think that I might pick up a more audiophile level second TT, at some point, maybe even a manual. It will probably be a belt drive because the really good DD tables are out of my budget. The summary: At the lower end of the price spectrum, I think choosing the drive system is secondary to the quality of the plinth, tonearm and noise isolation.
Found this video tour of the Thrax factory in Bulgaria that manufactures the Dohmann Helix turntable (the TT of the rich!).  Quite impressive and thought you might find interesting:

https://youtu.be/5QYu6qRg_PA