Okay, I have been thinking this over for the longest time. I'm gonna just point out different parallels with the DE/SE Vs. SB/BA triangles.

Angel/Stefan comparisons:

1) Both drink mostly animal blood.
2) They're very lethal, perhaps worse than Spike/Damon when on HB/without soul.
3) They have a similar hairstyle.
4) Both tend to go *forehead brooding*.
5) They make fast Friends with Buffy/Elena's friends.
6) They wanna fight the good fight.

Spike/Damon comparisons:

1) They're the *bad boy* vampires.
2) They used to (sometimes) be merciless when it came to humans, but have/are rediscovering their humanity....