Organized bicycle trips have the advantage that you can focus on enjoying the journey without thinking about the logistics of the trip, accommodations or meals. The main disadvantage is usually a higher cost and less flexibility to choose the departure date.
Self-guided cycle tours are more difficult and demanding, since you will have to plan all the details of the trip if you do not want to suffer unforeseen events. This type of adventure will give you a more realistic learning and experience at a lower cost.