VPI TNT Turntables

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.

I think we have gotten far afield of helping the OP with his decision or search.

@phoenixengr  Although your comments are appreciated by some including me, they will be far better appreciated if you identify yourself in every post by signing as a party with a commercial interest. 
It comes off pretty lame to read a string of posts that point to the benefits of your product without you telling us that you sell a product. 
FWIW, I've heard great feedback on your speed controller! No ill will intended. Cheers,
Spencer