Sprinters or Shamblers? I'd say it depends on the zombie's state of decomposition.
Personally, I'd rather take on a group of Shamblers than a single Sprinter. Though, I'd still be killed and eaten.
Now for my inane content!
Those newly reanimated would likely be able to sprint like in
Dawn of the Dead ('04), until rigor mortis set in. After a while, they'd start
shambling around like Romero's zombies.
Though, I am often told that rigor mortis eventually dissipates. So perhaps some of the Shamblers would pick up some speed and articulation (but not
much, being dead and all)?
Sprinters are frightening in that they can move quickly, and are loud, but in theory would "burn out" faster since the muscle's energy would be
spent quickly and unable to replenish; all that running would break down the muscles in the legs, unable to build back up even when at rest. After a
few chases, that strong, fast zombie becomes weaker and slower.
But Shamblers, even in large numbers, could be quiet enough to sneak up on a person. The rule above holds true for Shamblers as well, only they might
last longer, since they work at a slower pace. Of course, some Shamblers are so badly decomposed, it doesn't matter how strong they were in life.
The environment plays a part as well in decomposition, just like any other corpse. A zombie in a hot and humid region would rot faster than one in a
cold and arid climate.
In my opinion, concerning movies like
I Am Legend,
28 Days Later (and sequel), and
Quarantine, they are not zombies. Good
movies, yes, but not zombies. (You have to die and reanimate to become a zombie, and none of the victims in those movies do that, if I recall
correctly.)
Just my 2¢, whatever it's worth.
EDIT: Concerning the zombie's intelligence, I suppose that would depend on the condition of their brain as they decompose. I believe the zombie
would become more and more brain damaged as they decomposed.
[edit on 29-3-2009 by FreddyAuratus]