Why do turntables sound different?

To defend Ralph against myself, though I only attack him when he is advertising, he is not alone who thinks that modified Technics SP10-MK III with the right arm, cartridge and phono comes very close to the tape sound. I just wonder if top belt drive tables were involved in those comparizons. I think, not sure, that when Fremer was evaluating the Continuum Caliburn he actually said exactly that - closest to tape, and so he got it for himself.
It's easy to choose an open reel deck - just get Studer A80 or 810 or Ampex, and if you cannot any of those - Otari. But with turntables, considering that there are many, it's not easy even if you can audition them. But yes, I would actually compare any table with my deck. In other words, even if you are not going to use the deck, you need it to choose a turntable ! And possibly speakers too. In fact, anything. I don't think many do it this way but maybe more than I would expect.

Anvil, With reference to direct-drive turntables, you wrote, "Coupling a motor to the platter, in my estimation is a compromised design."  You are not the first person in your industry to make such a distorted statement, so I am sensitive to it.  In a direct-drive, the platter IS the rotor of a motor that has its stator mounted symmetrically around the spindle.  There is zero possibility for the coupling to introduce noise, except for the noise of the bearing itself.  Bearing noise is a bugaboo common to all types of turntables. Quiet operation is a virtue of direct-drive, not a problem.  DD introduces other possible issues, but not that one.

As to your statement about DD lacking microdynamics, this can happen if the motor causes counter-rotation of the stator, because of the hi-torque forces involved. (Motor drives platter in clockwise direction but its torque exerts an equal force in the counter-clockwise direction. Per Newton's Third Law of Motion.)  If a tiny amount of counter-rotation of the motor or its parts occurs, this results in a perceived speed error by the servo, and the servo exerts a correction.  Thus there can be a constant hunting for speed on a very micro level that is not readily perceived as pitch error but as a loss of detail or a mechanical sound.  This is why DD turntables do best in massive plinths, IMO.  But also, Richard Krebs has addressed the issue for Technics tables with his internal mods that reduce the capacity of the stator to rotate against its own force.

I don't waste my time arguing for one turntable technology uber alles.  I have found what I like, and I plan to stick with it.  Probably the same is true for others participating in this thread who champion other drive technologies.  

Inna et al, Like any top dogs in any field of endeavor, both the Continuum Caliburn and the Rockport Sirius have their detractors, even among belt-drive aficionados.

I would also think that the belt in the belt drive design should be very important. It's like a cable, in a manner of speaking, that connects two components. 
I can even imagine that at this level my preference might depend on a particular music and record, so I would take both the Continuum and modified Technics, no need to choose, really.

This is a bit of an Oxford Entrance Exam question, but IMHO and in short:

1. Drive mechanism - affects timing fundamentally - the amount of vibration transferred into the playback and indeed the type/cycle of vibration;
2. Platter - channeling of resonances from the record - also relevant to speed stability and is fundamentally linked to drive mechanism
3. Plinth/suspension - again vibrations both from the record, platter, bearing, and room born
4. the arm - energy transference from cartridge; cartridge match; resonance control

It is arguable that almost everything has an affect on the performance between decks. Just compare the various Linn Sondeks which have seen generations of change - new top deck; bearing; motor, and power supplies. For instance some arms are too heavy for the suspension on the LP12.

What is more interesting is when you have two totally different decks that sound almost the same - but I guess that brings around another whole new topic of discussion ;)

I have pondered whether or not all decks should all aspire to have the same sound, but I think being neutral and altogether accurate is an impossible ideal - why you ask? Well a full rock band, let alone an orchestra can fit in the average persons living room - so how can we expect all-together accurate replay of that very thing?

@lewm,

"lubrication is made more effective as well on a smaller tighter tolerance contact also,"

I agree. Just take a look at the newer automobiles with tighter cylinder/piston tolerances that use thinner viscosity oils...