See with Zombies the real choices are Zombies or Zippys. Zombies are your typical "Dawn of the Dead" fare, Zippys are the ones in "28 Days Later" they move much faster
Actually in the original Dawn of the dead they have what is now known in the film industry as slow zombies. The New dawn of the dead brought forth "fast zombies" that have carried on to "28 days later"...