Direct Drive vs. Idler Drive vs. Belt drive

@chakster
After re-reading the above, I think you are right!  :)

Everyone I know with either an Sp10Mk3 or Sp10R is using an aftermarket platter mat of some type and not the supplied rubber mat. 

Agreed, either the Micro Seiki CU180 or more rare CU500 Gunmetal Copper alloy mats would be ideal for the job.
In this country (US) Gunmetal alloy is more generally expensive and harder to obtain than pure Copper, but in many countries it is the opposite.  I own a Gunmetal Copper Micro Seiki CU-180 which I have compared to the Artisan Fidelity pure Copper Universal platter mat which I use sometimes on the Kuzma Xl DC, and they are similar, but the later can give some recordings a touch more weight and "body" if you will, to the sound.  My thoughts here are it may be because gunmetal contains 88% Copper, 10% Zinc and 2% Zinc (est.) while the pure Copper mat does not contain the additional metal alloys.   

scar972

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.

Many insightful responses above from knowledgeable, well established members. Over the decades, I can state with confidence that I thoroughly enjoy all drive types in my own system and each are represented at very high level. The execution of the drive and overall engineering integrity have a tremendous influence on playback. Honestly, I think they all have merit and any (Belt, Idler, Direct) drive platform when properly implemented can serve as a true analog point of reference.

88% Copper, 10% Zinc and 2% Zinc

Corrected typo. 

Gunmetal - 88% Copper, 10% Tin and 2% Zinc (typically)

neonknight

"Even if the platter replaced with thicker and heavier one those guys always add copper mat on top of it, just like the latest Technics SP-10R."

The Technics Sp10R's main platter was designed to be used in combination with a platter mat, like the supplied factory rubber mat or an aftermarket metal based mat (ie. Copper, gunmetal, stainless steel, delrin ect.)
As shown in the poster link, that Sp10R platter was photographed in the "nude" without a mat installed.  The material section at the top is a brass alloy, and not Copper.