Formal education/training tends to deal with theory and intellectual understanding. Informal education tends to deal with experience and intuitive understanding. (These are broad generalizations, certainly not absolute or precise.)

My experience has been that the most efficient learning comes from a combination of training and experience. Learning theory is dry and academic without experiences to apply it to. Learning by experience is often haphazard and frustrating without theory to guide it. Either one by itself can get you a far way with enough time, but put the two together and you can really make tracks.