Clash of the Titans: The Ghost vs the Serpent

Both the Ghost and Claudius can be identified as suspicious and sly characters.  The Ghost claims that Claudius had murdered him, which puts Claudius in the spotlight as the murder of the past king.  However, why would the Ghost urge Hamlet to commit a sin, by murdering Claudius, while he is in purgatory, a place where sins must be washed away before one can go to heaven.  Despite this suspicious behavior, the two character's speech severely contrast one another.  The Ghost is very frank when speaking, and tells Hamlet exactly who murdered him “the serpent that did sting they fathers life now wears his crown” (742).  Conversely, while Claudius is also quite literal in his speech, he speaks in a roundabout way and uses a lot of "fluff" words before stating his point.  In his main speech addressing the death of his brother, the previous king, Claudius hints towards his marrying of Gertrude, but does not directly address it until the end of his speech.