I don't know the answer to this one, which is why I am asking. Rufe0 says that servos with encoders need to microstep to achieve high positional resolution. I assumed that the reason for things like 2500 line encoders was to achieve (approximately) the same level of resolution as, say, 12 cascaded 200-step steppers with rather less rotational inertia. Do servo systems microstep? I've never worked with servos so have no experience of how they and their drivers are set up. I do assume that there will be a small amount of rotational uncertainty as the servo hunts between two adjacent encoder lines, but I can't believe that this is any worse than the rotational uncertainty of a stepper under varying load as it only generates a restoring torque when displaced by some (very small) distance from the exact "step" position.