I was reading Sam Vaknin's thoughts on possible co-morbidity of narcissism with different personality disorders, including sociopathy:
As opposed to patients with the Borderline Personality Disorder, the self-image of the narcissist is stable, he or she are less impulsive and less self-defeating or self-destructive and less concerned with abandonment issues (not as clinging).
Contrary to the histrionic patient, the narcissist is achievements-orientated and proud of his or her possessions and accomplishments. Narcissists also rarely display their emotions as histrionics do and they hold the sensitivities and needs of others in contempt.
According to the DSM-IV-TR, both narcissists and psychopaths are "tough-minded, glib, superficial, exploitative, and unempathic". But narcissists are less impulsive, less aggressive, and less deceitful. Psychopaths rarely seek narcissistic supply. As opposed to psychopaths, few narcissists are criminals.
Patients suffering from the range of obsessive-compulsive disorders are committed to perfection and believe that only they are capable of attaining it. But, as opposed to narcissists, they are self-critical and far more aware of their own deficiencies, flaws, and shortcomings.