Bubba, the digital servos have an amplifier that updates the motor with the stick position 3 or 4 times as fast as an anaolog amp. Speed and torque is more a function of gearing than servo amp, there's cheap digitals and good analogs.

The fact that the update pulse occurs more often is why they use more current.

Here's a white paper from Futaba on the details.

http://www.futaba-rc.com/servos/digitalservos.pdf