Jason Fried writes in Inc. Magazine…
Resumés reduce people to bullet points, and most people look pretty good as bullet points… Cover letters say it all. They immediately tell you if someone wants this job or just any job. And cover letters make something else very clear: They tell you who can and who can't write. Spell checkers can spell, but they can't write. Wordsmiths rise to the top quickly. Another rule of thumb: When in doubt, always hire the better writer."