Uber, This is all nothing but my opinion based on owning two consecutive Lenco L75s, one that I bought from John Nantais with one of his heavy plinths and his other tweaks, and the other that I bought absolutely stock (NOS) and tweaked myself. First, I never listened to my NOS L75 before modifying it, but most experienced Lenco persons say the OEM unit can sound very good, with the Achilles heel being the tonearm. Yet, there are those who defend the tonearm as at least being OK. I really liked the Nantais Lenco, but I was bent on building one with a slate plinth, so I sold my Nantais version and had created a slate plinth for my OEM Lenco, using a 65-lb slab of Pennsylvania slate and the pattern provided by Peter Reinders (do a search on that name); it was cut with a waterjet using Peter's pdf file to program the machine. I then also purchased a massive aftermarket bearing made by "Jeremy" in England. I had the platter painted with a thick coat of vibration-absorbing paint, and I further dampened it using large O-rings stretched around the circumference, below the playing surface. Last, I regulate platter speed using the aforementioned Phoenix Eagle PS and Roadrunner tach. You don't have to do all or any of these things to get a nice sounding turntable for the cost of an L75 alone. I paid $500 for my NOS one, but good used ones are typically around $300, or at least they were, back then. I would say that my slate Lenco stacks up along with all my DD turntables except the SP10 Mk3 and the L07D, but the differences are not night and day. The latter two DDs are just a bit more completely neutral. You should go to the website "Lenco Heaven" for more information.
13blm, In my opinion, there are two basic schools of turntable design: heavy platter/weak motor vs relatively lightweight platter/strong motor, typically with speed regulation. As you and others have said, the heavy platter itself provides a form of speed stability due to its rotational inertia. Also "weak motor" always means belt drive, because the motor of a DD would have to be very powerful in order to motivate a heavy platter, e.g., the Technics SP10 Mk3 with its 21-lb platter and massive hi-torque motor. Avid turntables are examples of belt drives with relatively light platters and strong motors. Most other high end belt drives are massive platter/weak motor types. (If you want rotational inertia to keep constant speed, you don't want a powerful motor that can disturb the equilibrium.) Also, with a belt drive, you get the mechanical advantage of the small pulley driving a much larger wheel (the platter), and therefore a weak motor can work. I don't like blanket statements, like a heavy platter is always better. It depends upon how you want the speed to be maintained.