The suspension system needs to be damped, else the chassis will continue to bounce up and down well after the inciting force has passed. The designer also needs to tune the suspension so as to filter out frequencies around a certain set point. These choices and how they are achieved have major effects on the outcome. Also, suspensions can limit the weight of the tonearm that can be used, because the tonearm can cause the suspension to sag eccentrically. (In fairness, SOTA has a nice way of getting around the problem.) But finally, once you have a suspension, you have to worry about where and how to mount the motor. If the motor is not also suspended, then when the suspension is flexing it is also changing the length of the flexible belt. And the belt would have to be flexible to permit this action. Stretching of the belt leads to very audible pitch variation, and stretchy belts also increase "belt creep". Early SOTAs were very prone to this problem. So then the motor needs to be mounted ON the suspended part of the chassis (as SOTA does do these days, or so I am told), which means that its vibrations and noise are right on board with the springy suspension. Also its mass, which is another source of unbalance and sagging. Yadayada.
