how does Stevenson present the differences between Jekyll and Hyde?

Jekyll himself has two personas, a private persona and a public persona. In public, he is known as a doctor, loyal friend, a man of intelligence, and a benefactor for those in need. Privately, he yearns for the freedom to do all of the things that would tarnish his public reputation. Jekyll is around fifty years of age; he's a big man and clean shaven. Utterson describes Jekyll as deeply religious and charitable.

Hyde is self-serving, selfish, brutal, and destructive. He is angry, uncaring and detached. Without conscience, he feels no remorse for his violent acts. None-the-less, he's like a child in his fear of being found out..... driven to tears over thoughts of the retribution he might one day have to pay. Hyde's hands are described as gnarled, and although he's a small man, he's wound up with energy.

These two men represent two separate personalities, and as we later find out, one will be forced out in order to allow the other his freedom.