Lau vs. Colin - Yan vs. Billy

I just watched this film tonight and I thought it was interesting how the depiction of the two main characters was altered in The Departed.

The central question in IA seems to revolve around Lau--is he good? is he bad? There is a kind of heroic ambiguity to him. On the other hand Matt Damon's character (Colin) in The Departed is completely unlikeable--he turns out to be an improbably sniveling whimp, his macho persona stripped away at the end of the film. It almost feels like a commentary on an archetypal spineless social climber.

I think Yan and Billy (Dicaprio) are more similar. Both characters are essentially heroic, but I think Yan ultimately comes out looking better--his motives seem more pure. Dicaprio plays Billy with such deadly seriousness and paranoia that he becomes kind of whiney and unrelatable. Also, Billy's totally egregious use of the word *beep* on the rooftop at the end highlights the fact that, though he is 'doing the right thing,' he's far from enlightened. You begin to wonder if he knows why he is doing the right thing.

I guess I would say that Scorsese resists the urge to romanticize and resultantly his characters are less cohesive and categorizable, ultimately less satisfying in a direct, emotional kind of way.

Any other thoughts on the differing depictions? Is there an ethnic/societal element at play perhaps?