One advantage and disadvantage (at the same time) is that printed communication is a permanent record of the communication. Perhaps that isn't necessarily always the case. A person might burn a letter, but the main reason to write something down is in order to keep it for some kind of record. That quality of printed communication is extremely helpful, especially for certain kinds of communications or transaction, such as during tax season for example. On the other hand, some print-preserved communications could cause unintended negative, troublesome consequences. For example, a message sent out in anger might prove detrimental to a relationship of the personal, political or business kind.
One advantage to printed communication is that it gives the writer time to reflect and collect his or her thoughts. There are times when communicating verbally or electronically that things can be said that out in a way not intended. But with printed communication, more time and care is spent making sure what is written is exactly what is intended.
A disadvantage to printed communication is that in order to reach a lot of people at the same time, a lot of it has to be produced. That can be quite expensive. The expense can be overcome by digital communication, but digital cancels the advantages of time and care.