Digitals use all of their energy to find a position; they are either on or off, hence 'digital'. This includes trying to find the center position - they use all of their energy to hunt for the neutral/center position. Analog servos use less energy but are absolutely fine for sport flying. To me, flying a plane with digital servos feels more 'crisp', responsive, and precise. I have 3 planes, and am pretty much only using analogs for throttle - because I already have them.