What are the true faces of Alec and Angel in Tess of the d'Urbervilles? How are they similar and different?
By "true faces" if you mean what are Alec and Angel's true intentions or character, they are the following.
Alec certainly does not sincerely care about anyone else but himself. He seeks pleasure, and Tess is simply another pawn in his quest. Later in the novel, while Tess seems to mean something more to him, it is more of an obsession with her than it is concern for her or a true appreciation of her character.
Angel truly does care for Tess and others and is not completely wrapped up in his own goals. In the end, he demonstrates some of his honor by taking care of Tess's sister.
While Angel would not physically rape Tess as Alec does, he is guilty of using Tess, thus his similarity to Alec. Hardy uses the two men--though quite different in their natures and in the feeling they inspire from Tess--to demonstrate that Tess is a victim of fate. Even when she meets someone whom she cares deeply for (Angel), fate allows him to use her emotionally and to drain all hope from her.