¿Cual es la diferencia?
Magia is magic, the "true". Misterious and supra-natural powers.
Ilusionismo comes from ilusión ( illusion,) something that pretends to be the truth, but it's not. A trick
prestidigitación; comes from presti > quick, agile, and digitación ; to move the fingers = to move the finger fast, as happens with the so called "card's magic", and in general all "magic" that has to do with quick and hidden movements of fingers and hands.