The Form and Content of Mulligan (vs. Dedalus).

Though the formal experimentation in Ulysses has long been something I've expected, I was surprised by the style of the content. What I had expected was a surreal form and a hyper-real content, the book after all takes place throughout the course of a day and so because of this, as well as Joyce's stream of consciousness preoccupation which attempts to most accurately portray the human mind in a literary context, I had expected everything to be very realistic content wise. However from the very beginning the character of Buck Mulligan reads like an eccentric clown. He is referenced to as laughing perpetually, he takes Stephen and dances him around the tower, he puts on the religious facade and quotes ancient texts often more humorously than seriously. Particularly interesting is his contrast to the way in which Stephen's character is written. Very morose and dry, but not really to the point of an archetype or paradigm. Why do you think Joyce contrasts the styles in which the characters are written so much? They seem to not exist in the same world at times, still they work very well off of each other. Why is this? Will Joyce continue to do this with other characters/settings or occurrences through out the text? again, what is the purpose?