Macbeth - Act 1, Scene 4: How does the Old Thane of Cawdor's behaviour differ from Macbeth's behaviour as Thane of Cawdor later in the scene?
Of the old Thane of Cawdor, Malcolm, Duncan's older son, tells his father that
Very frankly he confessed his treasons,
Implored your Highness' pardon, and set forth
A deep repentance. Nothing in his life
Became him like the leaving it. (1.4.6-9)
In other words, the traitorous nobleman acted at least somewhat honorably in the end, more honorably than he'd ever behaved before. He did not weep and wail and moan; instead, he acted like a gentleman, and he told the truth in a confession of his wrongs.
Macbeth, on the other hand, has become treacherous and deceitful by the end of this scene. When he hears Duncan name Malcolm as the Prince of Cumberland and heir to the throne, Macbeth immediately begins to plot against his king and kinsman. He says to himself,
Stars, hide your fires;
Let not light see my black and deep desires.
The eye wink at the hand, yet let that be
Which the eye fears, when it is done, to see. (1.4.57-60)
He immediately begins to consider taking violent action, such that his eye would not want to see what his hand is doing; however, his hand will do it anyway. It sounds as though he is already contemplating Duncan's murder. Thus, the old Thane of Cawdor goes from traitorous to honorable and the new Thane of Cawdor goes from honorable to traitorous.