Having given digital servos an honest try when they first started becoming available, this is what I learned.
1. Digital servos are huge power hogs.
2. Trying to control digital servos on a radio not equipped with EPA will burn it/them up in short order.
3. Digital servos by design are not more powerful or faster than their analog counterparts, speed and torque are functions of internal gearing and motor amperage. Digitals simply read for and adjust to positioning input about 100 times faster than an analog which is what will cause them to burn up quickly if you try to run the servo past whatever physical limits are placed on it by your cars linkage.
4. Digital servos are more prone to problems stemming from moisture, vibration, and pounding than are analog.
5. A digital servo will produce much more heat than an analog servo with comparable speed and torque.
6. The idea behind digital servos is not more power and speed, it's precision and holding power. Great things for the large pattern planes they were developed for, not so great for hossing around a huge set of heavy MT tires.
7. Digitals servos are programmable, provided you are willing to drop another couple of hundred bones for a programming device.