Difference between using PWM/Servo shield and Sensor Shield

Projects General Guidance
1

I am making a robot arm with a master-slave controlling system and was wondering if there is an advantage to using this:

as opposed to this:

Thanks

2

One is intelligent (PCA9685), and the other one seems to be a "connectors only" shield.

A command writen to the PCA9685 is executed after that independent of the Arduino.
The Arduino is free to do other things (untill the next command).

Maybe better to use a breakout board instead of a shield if you plan to use more than 16 servos.
Multiple boards (with different addresses) can use the same two I2C lines.

Leo..

3

Wawa:
One is intelligent (PCA9685), and the other one seems to be a "connectors only" shield.

A command writen to the PCA9685 is executed after that independent of the Arduino.
The Arduino is free to do other things (untill the next command).

Maybe better to use a breakout board instead of a shield if you plan to use more than 16 servos.
Multiple boards (with different addresses) can use the same two I2C lines.

Adafruit 16-Channel 12-bit PWM/Servo Driver - I2C interface [PCA9685] : ID 815 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits

PCA9685 for sale | eBay

Leo..

The Arduino will only need to control the servos, no other tasks. Will there be a difference in performance? I will be controlling no more than 8 servos.