The written language can be significantly more precise. Written words can be chosen with greater deliberation and thought, and a written argument can be extraordinarily sophisticated, intricate, and lengthy. These attributes of writing are possible because the pace of involvement is controlled by both the writer and the reader. The writer can write and rewrite at great length, a span of time which in some cases can be measured in years. Similarly, the reader can read quickly or slowly or even stop to think about what he or she has just read. More importantly, the reader always has the option of re-reading; even if that option is not exercised, its mere possibility has an effect upon a reader's understanding of a text. The written word appeals more to a contemplative, deliberative style.
~Differences Between Oral and Written Communication
Vincent Ferraro and Kathryn C. Palmer
Mount Holyoke College
South Hadley, MA 01075
Speaking and Arguing: The Rhetoric of Peace and War