Cheap Japanese DDs eliminated potential belt issues but typically lacked both sufficient motor torque and flywheel affect. We used to fit the more massive aftermarket mats to good effect on both the lower end Technics DDs and BDs, back in the day; this for improved flywheel affect, more so than for improved platter/record damping.
Out of the box, there were really no performance differences between the lowest BD and DD models. Given time, the cheap BDs went off rather quickly due to their tiny motor pulleys necessitating that the belts be both tight fitting and of high elasticity; the latter a requirement in order to retain the belt round the inner drive rim during transit/storage, whilst also allowing for it to be easily stretched out over the tiny pulley (otherwise, Japan Inc. would have had to go for costly separate platter/sub-platter metal with stiffer belts, which wasn't on).
At the higher end, Japanese DDs were way out in front, having ample motor torque combined with somewhat greater platter mass. The PLL, and later quartz, speed control circuits were really just the technological icing on the cake; necessary to maintain a given speed, but not the overriding determinant of speed consistency (IYSWIM).