RE: Is a digital servo better?
If you have a servo with a fet lead, that means it's a 7.2volt FET servo. If you want to run them without an ESC, you need to run a 7.2 volt pack to power the servo. How you hook this up without frying everything depends on your equipment. Trust me, it's not worth the hassle.
Right now, I'm running a 6 volt FET servo (KO Propo) for steering in my Mad Force. With the 6 Volt FET servos, you treat them like a regular servo.