If you're talking about the time it happened in Season 2. I think the comparison is hilarious, though. Evil, soulless Angel acts in a very similar manner toward Buffy as Eward does toward Bella (watching her sleep, etc). Only in Twilight it's presented as romantic, and in Buffy it's presented as deeply disturbing.

Though Angel was using it specifically as an intimidation tactic and everyone knew he was out to kill Buffy at time, so that may change the presentation a bit. But not that much - in Twilight the idea that Edward may potentially kill Bella is harped upon at length, and he is a rather ambiguous figure at the beginning of the novel (even though there's never any doubt about what's going to happen). The romance aspect is present in Buffy as well, albeit in an extremely twisted and dysfunctional way.

The difference though is that Edward doesn't stop being a borderline stalker as he moves squarely into Good Guy Land. In fact, his possessive boyfriend tendencies intensify. As I read Breaking Dawn and Eclipse I couldn't help but think of the lessons I've ever been taught about identifying a potentially abusive relationship: actively discourages friendships outside of the relationship - check ... demands to know where you are at all times - check ...

Fascinating, isn't it?