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.
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.
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....