What contrast does Lord Henry make between Basil and Dorian in The Picture of Dorian Gray?

In the first chapter of The Picture of Dorian Gray, Lord Henry makes the following contrast between Basil and Dorian:

Basil...with your rugged, strong face and your coal-black hair, and this young Adonis, who looks as if he were made out of ivory and rose-leaves.

To put this into context, this contrast appears after Basil has shown the painting of Dorian to Lord Henry and has told him that he will not exhibit it. Basil explains this by saying, "I have put too much of myself into it," and this prompts the above contrast from Lord Henry. 

Lord Henry interprets Basil's comment as an admission of his perceived beauty. He thinks that Basil believes himself to be as beautiful as Dorian but he is, in fact, making an admission of his love. This reference to homosexual love is one of the reasons why the publication of Dorian Gray sparked such outrage among the Victorian public. Whether Lord Henry really appreciates the extent of Basil's feelings towards Dorian is not made clear in the chapter. It goes a long way, however, in explaining why Basil is so hesitant in allowing Lord Henry and Dorian to meet: he is possessive and protective because he is in love. 

We also learn something important about Dorian in this contrast. Not only is he extremely beautiful, his youth and vitality also strike Lord Henry, hence his comparison to Adonis. These characteristics are what enable Lord Henry to become such a strong influence on Dorian later in the novel and which ultimately bring about Dorian's demise.