Who is the stronger character--Macbeth or Lady Macbeth?

In Shakespeare's great tragedy, "Macbeth," the question of whose character is stronger--Macbeth or Lady Macbeth is not so easily answered.  For, on the one hand, Lady Macbeth is the force that drives Macbeth to commit his first heinous act, the murder of Duncan.  But, is it strength that she demonstrates or merely a lack of conscience at the moment and less contmplation of the act itself?  For, while Macbeth falters some as he perceives the bloody dagger before him, Lady Macbeth claims,

That which hath made them drunk hath made me bold/What hath quenched them hath given me fire. (II,ii,1-2)

Thus,it seems that her boldness is a result of knowing she has drugged the servants of Duncan, while Macbeth is emboldened by the ring of the bell, Lady Macbeth's signal.  Later, Lady Macbeth expresses fear that the servants may have awakened; she also states,

Had he [Duncan] not resembled/My father as he slept, I had done't. (II,ii,12-13)

When Macbeth returns, telling her that the servants cried out "Murder!" and "Amen" stuck in his throat as they prayed, Lady Macbeth replies,

Consider it not so deeply..../ These deed must not be thought/After these ways; so, it will make us mad. (II,ii,29-33)

Still, Macbeth is uneasy, explaining that he heard a voice cry, "Macbeth shall sleep no more" (II,ii,42).  He then tells his wife that he cannot look upon the daggers.  Angrily she retorts,

Infirm of purpose!/Give me the daggers.  The sleeping and the dead/Are but as pictures. 'Tis the eye of childhood/That fears a painted devil....I shame /To wear a heart so white..../A little water clears us of this deed. (II,ii,52-66)

This last line is, of course, ironic.  For, Lady Macbeth is unable to really not think of the deed as she has instructed Macbeth, nor can she use water to clear them of their murderous deeds.  In Act V, obsessed with guilt that she can no longer push out of her thoughts, she seeks to wash out blood that she imagines is on the stairs of the castle in Dunsinane.  The character who has accused another of weakness has herself gone mad because of her guilty feelings.  Despite her earlier conviction that she could push them away by simply not contemplating them, she is not strong enough to do so; her conscience gets the better of her, driving her insane and, finally, to suicide.

Who, then, is stronger?  If one defines strength as having the will to pursue one's goal despite its evil, Macbeth is, then, stronger because he continues on his murderous path toward power after Lady Macbeth succumbs.  If, on the other hand, one defines strength as moral integrity, Macbeth certainly lacks this much more than his wife.