There is a nuanced difference between coaching and mentoring.  Coaching involves a specific task in which individuals need orientation to completion.  There is a fixed end in coaching.  Completion of a project, taking initiative in a particular end, or a specific construct in which guidance and effort is geared.  The discourse between coach and individual is geared towards this end.  In the mentoring context, there seems to be a more open notion of the good.  Mentoring is wide open, geared towards the idea of fulfillment of a larger scope and context.  There is not the driven end that one sees in coaching.  Rather, mentoring is about "more philosophical, more focused on attitudes and behaviors than on specific skills."  Both are needed in the work setting as one focuses on the pragmatic ends of a job, while the other one helps to establish the foundation for potential happiness or contentment in a wider setting.  I think that this becomes the primary difference between the two and individuals at different points in their journeys will require both or more of one than the other.