As in the main title/credits song? I voted Angel. I found that the Buffy nerf herder song tended to wreck the emotional climaxes of many an episode by being used in the end credits. Just not a song you want to hear after some kind of tearjerk episode. The Angel song was less intrusive.
Have to agree with that.
I went with Angel. It fits the darker tone of the series perfectly. The "Close You Eyes" Buffy/Angel love theme is great stuff as well.