And 28 Days/Weeks Later had runners too (I know, they weren't "technically" zombies either...) and they were also great.
I think the running zombies look crazier. Seeing the swarms of blood covered "infected" running at the camera in the 28 films was pretty scary, more so than a load of people shuffling around moaning "braaaaaains". Although, my mate is of the opinion that the shambling zombies are scarier because even though they are slow and apparently stupid, no matter what, they will still get you. There's a certain logic there.