I think that the idea of how Whitman sees something internal as guiding the vessel of the soul and how Dickinson sees this guidance as external in each poem is a valid assertion.  I think that both poets are able to convey the need for guidance.  Interpreting the subject matter of the boat and the relationship between the moon and the sea as a statement about the contours of the human soul, both poems and poets stress that there is a need to find someone to lead or to provide guidance in complex situations.  For Whitman, this does come from internally, in terms of the steersman holding his mission to guiding the boat with the deepest of reverence.  One could argue that this is external, as well, in that the boat and the steersman are two separate entities.  Yet, Whitman is able to design it so that the steersman and the boat are one.  The steersman understands his purpose, his mission, in the clearest of ways in which he aligns himself with the boat, akin to a "ship within a ship."  This makes the connection between both seem as one, in which an internal connection and form of guidance can be seen.  For Dickinson, the sea needs the moon.  The sea's external form of guidance is in the moon.  Even though there is an externality here, Dickinson suggests that the relationship is so tender and so strong that it might as well be one.  In this conception, external guidance is so absorbed that it might as well be an internal one.  It is here where both visions of being led can be seen as Whitman's being internal and Dickinson's being external.  However, a case can be made for the opposite of being true in the manner that each poet has constructed the vision and need for guidance and help.  In the final analysis, I think that both poems show that if the soul is able and willing to receive guidance, internal or external support, can be absorbed as the full contours of the individual soul are defined and examined.