In what ways does Lady Macduff contrast with Lady Macbeth in Macbeth?

I don't think you could find two characters that are
actually more different. I think, however, the biggest difference that Shakespeare
creates between these two characters is the way that Lady Macduff is explicity presented
as a mother figure in the one scene in which she appears in Act IV scene 2. She is shown
to engage in some pleasing banter with her eldest son, which is obviously designed to
make the audience feel sympathy for her and her situation. In addition, when she is
given news of the approaching murderers, note how she
responds:

readability="21">

Whither should I
fly?

I have done no harm. But I remember
now

I am in this earthly world, where, to do
harm

Is often laudable; to do good,
sometime

Accounted dangerous folly: why then,
alas!

Do I put up that womanly
defence,

To say, I have done no
harm?

Note the innocence
expressed in her character through her response. She is deliberately presented as a
good, perhaps somewhat naive, mother figure, who loves her
children.

Contrast this impression with Lady Macbeth, who
talks happily about smashing the head of her babe and can not be described as naive at
all. The power of Lady Macbeth lies in the way that she is able to manipulate both her
husband and others through a mixture of mockery and pleas. Whereas Lady Macduff is an
honest and good character, Lady Macbeth fears that her husband is "too full o'th'milk of
human kindness" and famously, in Act I scene 5, asks the spirits to make her into even
more of an evil character than she already is:

readability="11">

Come, you
Spirits

That tend on mortal thoughts, unsex me
here,

And fill me, from the crown to the toe,
top-full

Of direst
cruelty!

It is interesting
that Lady Macduff is a character that we associate with feminine motherhood, whereas
Lady Macbeth, having no children and being asked to be "unsexed" here, stands in
complete contrast to Lady Macduff.