What are the similarities and differences between Hamlet's and Macbeth's moral decisions in the plays?I am interested in considering what they...

I think it is very thoughtful to consider the actions of
Hamlet and Macbeth as active choices that they make.  This, of course, implies that
there are other choices that they could have made.  I'll give a few comparisons that
spring to mind, to help in  considering the question.  But there is no one answer.  You
must discover what strikes you as important.

First, both
Hamlet and Macbeth decide to commit murder.  The circumstances and the amount of time
spent debating this course of action are where they
differ.

Macbeth is not alone in his choice.  The
determination and strength of his wife plays a huge part in his choice to kill the
king.  The morality of this decision is definitely in question.  Macbeth reasons to
himself that, since it was foretold that he would be king, how wrong could it be to help
events along a bit?  Again, Macbeth may have, acting on his own, been more cautious, but
Lady Macbeth drives the action forward in order to strike while they have Duncan under
their roof.  In Macbeth, the murder happens in Act Two, scene
one.

Hamlet's act of murder is also one of revenge:  He
must kill the murderer (his uncle) of his father.  Like Macbeth, he is spurred by
another to commit the act.  In this case the instigator is the ghost of his father. 
Hamlet is very cautious in this regard.  He questions whether the ghost is an agent of
Heaven or Hell.  He questions whether, in murdering Claudius, he might send him to
Heaven, instead of Hell where he belongs.  And he questions Action itself.  Most
notably, he alternates between chiding and laughing at himself for not being able to do
that which he knows he should do.  It takes him the entirety of the play to decide to
act.

So here's a huge difference:  Macbeth knows in his
heart that the murder he commits is wrong, while Hamlet cannot decide whether it is
right or wrong, and is really only able to commit the deed when he becomes enraged at
the poisoning of himself and his mother at the end of the
play.

It should be noted that morality is sometimes an
issue of culture.  Revenging the murder of family members is still common practice in
many cultures today, and was a popular topic of plays in Shakespeare's day.  The
character in these Revenge Tragedies, whose job it was to avenge the death of a famly
member, were considered the heroes of the plays and, once the act was committed, justice
was considered to have been served.

So morally speaking,
and as the question of what acts should have been committed by Hamlet and Macbeth, there
are many things to consider, and, ultimately, the choice is
yours as the audience member.  What do you think they
should have done?