For many analogue servos have been the choice particularly for the sport flier, and traditionally digital servos have been much more expensive. But now we have deals such as this that have put quality digital servos within the reach of everyone why go digital? Analogue and digital servos are exactly the same but with one important difference and that is the way the signal is processed and sent to the motor. A microprocessor in the servo analyses the receiver signals and processes these into very frequency voltage pulses to drive the servo motor. A typical analogue servo may send 50 to 100 pulses every second, but with a digital servo this can be up to 300 pulses. This typically results in faster, smoother response, smoother acceleration and deceleration, and very importantly greater holding power i.e. less chance of 'blow back' on a control surface in extreme situations, a digital provides improved speed and torque when it is needed most.
And the drawbacks of going digital? Well not a lot really but the main one is that because digitals are essentially 'always on' they can be a bit more power hungry so you may want to factor in slightly larger power packs to account for this.
And finally to answer the two most common questions we get - No, you don't need a special radio set to use them, and Yes you can mix analogue and digital servos quite happily in an installation.