VPI TNT Turntables

Fwiw I would rather have continuos speed than ever changing speed. But we've gotten into this before. 
The ear will detect changes much more easily than a controller that is slightly off but the same all the time. 

Constant motor speed does not equate to constant platter speed however.

Would you rather have constant motor speed with constantly changing platter speed, or motor speed that changes to keep the platter speed constant?

With respect to the effect of a flywheel, I believe (my physics are quite rusty, about 40 years rusty) the important effect is Angular Momentum and the Moment of Inertia, both of which are directly influenced by angular velocity.  Moment of Inertia also feeds into the torque of a rotating object, once again angular velocity is directly related to torque.  The flywheel acts as a torque multiplier, something the relatively small motor needs.  Also, keep in mind the VPI flywheel is turning at a higher speed than the platter.  I can't speak to the dual motor flywheel, but I have the single motor flywheel and while I haven't measured it's speed (and couldn't find anywhere in a quick search that listed it) it is several times that of the platter.  This further increases it effect beyond what one might expect.

Now if only Brf would chime in we might get a more definitive answer!

If consistent motor speed doesn't equate to consistent platter speed how can inconsistent motor speed equate to consistent platter speed??
Why would the motor speed on your unit be inconsistent????

wait for it

wait for it

oh because the platter speed changed!

oh because the platter speed changed!

By the time you realize it, or your feedback system realizes it to try to adjust for it, it is too late. An adjustment can "adjust" for it after the fact, but it will not really "correct" it. The cat (or error) is already out of the bag.  I guess this lag between finding the error and trying to adjust for it after the fact could be minimized if the sampling was more frequent. Better would be to have an inherently accurate and precise setup. But difficult or impossible to do.