I'm much better at communicating with the written word than the spoken word.
When I'm speaking, I grope for the right words/phrasing, I go off on tangents, lose track of my own point, ramble on in far greater detail than needed . . . When I write, I can avoid those mistakes. For example: without this mention of it, none of you would know that, in the middle of typing this, I went off on a 5 minute tangent about a verbal faux paux I made in a recent conversation with an acquaintance, and how I could have avoided it. Also, I tend to make my point and then provide supporting arguments. A reader can skip the supporting arguments if they want, while a listener is kinda stuck waiting till I finish. And lastly - I tend to speak (and write) more formally than most. In conversation, the use of complex, grammatically correct sentences organized into paragraphs seems to confuse people, while it is just accepted in written communications.