“And he gave the apostles, the prophets, the evangelists, the shepherds and teachers, to equip the saints for the work of ministry, for building up the body of Christ, until we all attain to the unity of the faith and of the knowledge of the Son of God…” (Ephesians 4.11-13a)
Notice the variety. While a common goal is shared, “for building up the body of Christ…”, the roles are diverse. Why? Because there is a difference in those roles. Evangelists do not have the authority of apostles, nor the direct revelation of prophets. The tact between these roles is different, even while attempting to accomplish the same work. Likewise, all of these leaders use the same message, the Word of God, which we are also told is to be used in a variety of ways. “preach the word; be ready in season and out of season; reprove, rebuke, and exhort, with complete patience and teaching.” (2 Timothy 4.2)
Preaching a sermon is broadcasting a message to a select audience with limited feedback. Without a message conveyed back the speaker he could continue to talk without having any of the message received or understood. Teaching allows for a dialogue, thus allowing the presenter to ensure that the receiver has gained understanding. Writing allows the writer to examine every word to allow for the most precise rendering of a lesson. What is my point? Some lessons are better given in different ways.
Preaching can just as easily be done AT people as TO them. If, while preparing a lesson on adultery, the preacher knows of a congregant who is engaged in that activity, the sermon delivered will feel like an attack. Some lessons are long and require much examination of context before points can be made. Constant interruption of questioners will defeat the ability to present the information in a timely manner. These principles are better conveyed by one presenter. Sometimes the message is just not long enough to take up a 30-45 minute block. Write it out. Regardless of what you are best at there is a medium for you to tell others about the saving power of the Son of God, or to build up those who know Him. So, fan into flames the Spirit of God in you, and be heard (or read).