I'm a Romero man, myself- even though his zombies can't run up and tackle you (they can hit you with a rock, though
) their tendency to gang up and overwhelm people seems more frightening. Not that the O'Bannon zombies don't do this, but with the slow-moving Romero ones it feels like a big moaning wave, and just kind of makes you feel hopeless all over. Terror is easy to achieve in film, but sheer despair is not.
I totally agree, there's nothing better than a zombie movie for scares. Dawn of the Dead's my favorite, but second runner-up's Dead Alive (or Brain Dead, depending on what video store you go to). I beg and implore all zombie fans to see it, if you haven't already- you won't be disappointed! Just don't eat while watching it.