I think that their virtues are pretty similar. They're both heroic and steadfast in their heroism. They're willing to use their immortality and powers to fight evil. To be honest, it's not something I'd personally choose to do - I'd stick to hanging out with vampire erotica obsessed teenagers, loud music and video games. Yes, I'm basically Harmony, deal with it.
Angel's flaw is his raging paternalism. Angel still thinks and perceives the world like an asshole from XVIII century which is especially ridiculous considering the importance and prevalence of powerful women in his universe.
Spike's flaw is his clinginess or rather his almost comical, considering his rebel persona, need for validation. The women he loves, the idols he worships - like a sad puppy Spike wishes to be petted. Spike wants to belong, wants to fit in, even with the people who initially loathe him.