Perhaps the most apparent is to increase precision, which really is a function of manufacturing and assembly tolerances, gear tooth low backlash planetary gearbox surface finish, and the guts distance of the tooth mesh. Sound can be affected by gear and housing materials in addition to lubricants. In general, expect to pay out more for quieter, smoother gears.
Don't make the error of over-specifying the motor. Remember, the insight pinion on the planetary should be able manage the motor's result torque. What's more, if you're using a multi-stage gearhead, the 
output stage should be strong enough to absorb the developed torque. Certainly, using a better motor than necessary will require a bigger and more expensive gearhead.
Consider current limiting to safely impose limits on gearbox size. With servomotors, result torque is a linear function of current. Therefore besides safeguarding the gearbox, current limiting also shields the electric motor and drive by clipping peak torque, which can be from 2.5 to 3.5 times continuous torque.
In each planetary stage, five gears are concurrently in mesh. Although you can't really totally remove noise from this assembly, there are several methods to reduce it.
As an ancillary benefit, the geometry of planetaries fits the shape of electric motors. Thus the gearhead can be close in diameter to the servomotor, with the result shaft in-line.
Highly rigid (servo grade) gearheads are usually more costly than lighter duty types. However, for rapid acceleration and deceleration, a servo-grade gearhead may be the only wise choice. In such applications, the gearhead could be viewed as a mechanical springtime. The torsional deflection caused by the spring action adds to backlash, compounding the effects of free shaft movement.
Servo-grade gearheads incorporate many construction features to reduce torsional stress and deflection. Among the more prevalent are large diameter result shafts and beefed up support for satellite-equipment shafts. Stiff or “rigid” gearheads have a tendency to be the most costly of planetaries.
The kind of bearings supporting the output shaft depends on the strain. High radial or axial loads usually necessitate rolling component bearings. Small planetaries could manage with low-price sleeve bearings or other economical types with fairly low axial and radial load capability. For bigger and servo-grade gearheads, durable result shaft bearings are usually required.
Like the majority of gears, planetaries make sound. And the quicker they run, the louder they obtain.
Low-backlash planetary gears are also available in lower ratios. Although some types of gears are usually limited to about 50:1 or more, planetary gearheads extend from 3:1 (single stage) to 175:1 or more, depending on the amount of stages.