There's a 4th option, namely that Angel wasn't (directly) responsible for the deaths of the Slayers but that he is responsible for not doing more to save them. Twilight has been the evil funhouse mirror of Buffy all season. Now it looks as Buffy's mistake was to choose to let herself surrender to the glow ("Don't you want to be happy"). I suspect that Angel did the same thing earlier and with far more conviction. I kind of hope so because if we're talking Glowy Phoenix Angel that's my feminist revenge on X-men3 finally achieved.