Here's an excerpt from a great essay comparing the characters of Spike (William the Bloody) and Angel (Angelus).
Spike Versus Angel by Eleanor Kuhns
Transformed to a vampire, (Spike) becomes part of Angel’s coven, and for the first time, he becomes part of something. He has his own little family and is too scary to be mocked. Recalling his experiences with Angel and Drusilla during the Russian Revolution, Spike tells Buffy that it was the best time of his life. His wistful regret for a happy time that has passed really resonated with me. He is never really happy again.
Angel, on the other hand, never worries about fitting in. Why should he? He is always the leader. As a vampire, he has a rep as the baddest of the bad, with no pity or remorse. But when he reforms, he reforms all the way, becoming, to my way of thinking, a little self-righteous. He strides through the episodes like Cotton Mather in a leather coat. Yet, when he loses his soul, he becomes über evil. There are no gray areas with Angel.
Spike is a mosaic of gray. He certainly never achieves Angel’s almost arrogant level of self-confidence. In fact Spike remains always insecure, a feeling he covers with a flippant swagger. He wants someone to love him, first Drusilla and then Buffy, but never succeeds in attaining the relationship he wants. He wants to fit in but he just can’t manage it. Not and stay who he is. He wants to be good but only sometimes and not yet. Totally understandable.
Buffy the Vampire Slayer is a multi-layered show with many strands that explain its popularity and its following even now. And Spike is certainly a big part of it. He is villain, hero, and antihero all at once. In the final episode, Angel expects to save the world by sacrificing his life. After all, he is the hero and the good vampire. But it is Spike, the very flawed character whose journey we have shared, who is chosen. And that feels right.
My own feeling is that Spike becomes a true hero - the "champion" at the end of the series - not just because he is more complex, but because he makes a conscious choice to "be a better man" and get back his soul. Angel, of course, has a soul at the beginning of the series, but only through the gypsy curse - he never sought it out. Both characters suffer terribly and struggle with right and wrong - with backsliding, and even murder - but I agree with the essayist that Whedon got it exactly right in the end ~ Spike's journey is more noble for it being more unlikely.
