When plotting Banquo's murder, Macbeth acts much different then with the murder of Duncan because when talking with the murderers he acts very certain about his decision. This scene emphasizes that neither of the Macbeths is happy after attaining the crown.
Macbeth certainly does feel paranoia and guilt after Duncan's murder. However, as the play progresses, he doesn't hesitate to murder again to achieve his goal of beoming king. After he orders Banquo and Fleance's murder (He perceives them as threats to his goal), Banquo is killed but Fleance gets away.
