Why do turntables sound different?

The phono system of your hi-fi is just that, a system unto itself.  The turntable, its physical relationship to and with the room, the arm, the cartridge consisting of a stylus and electrical generator, and the load on the cartridge together make up a unique and one-of-kind electrodynamic system.  Change any element of that system and you will change, sometimes only in very subtle ways, the final aggregated performance of such a system.

Unfortunately each element of the system is also a bit different than supposedly equivalent or same element.  Replace any element in your phono system with an identical element, say the arm with another arm of the same make, model, and age, and you will be changing the dynamics of the reproduction system.  You may or may not hear the difference, but it is there.

Since the chain of events goes from the room on one end, and the cartridge loading on the other with whole bunch of subtle mechanical links in between, this is a gestalt where the whole is greater than just the sum of the parts.

There is no formula for audio GESTALT, so science is not going to jump on that band wagon.

Mankind science is a finite observation of infinity.  We can only hope infinity in the long run, will have its day in court.

So for this finite point in time, using our ears, is the best final judge for our own gestalt systems.

Bearing friction plays a large role in a decks subjective sound with higher friction designs often but not always imparting a dark, slow signature.  "Stretchy" rubber belts also are responsible for this type of sound. 

Bearing friction..
Anyone experimented with different oil? I didn't. I just use Nottingham's oil that they make for their tables. The sound is on a warmer slightly darker side and there is nothing slow to it. Belt is like new, doesn't feel or look wrong, only about 600 hours on it.

You were wondering why tables sound different. I mentioned the bearing because it is an often overlooked component that enormously contributes to sound quality.