Walkers are far scarier, it's the threat you can run away from but never escape. Walkers grind you down slowly, you can survive until there is no food, no chance of rest, and a mistake is made.
I don't agree with those saying that slow moving zombies pose less of a threat to the military than runners. If you compare the running zombies in the DOTD remake with the traditional Romero zombies there is a big difference.
The Romero zombie literally only works because it is established that the bodies of all recently deceased suddenly returned to life and immediately began to attack the unprepared living. There was no warning for this, lines were not drawn, troops were not mobilised, they literally appeared everywhere at once in numbers and started biting their family, friends, coworkers. With as little as 24 hours notice and some clarification that they are dead and cannot be helped, they never would have even posed the slightest threat. It is a commonly accepted fact that all zombie fiction exists in a universe that does not have zombie movies/games/comics.
In the DOTD remake it appears that those who die from anything else than bites do not reanimate. This means that in this universe an individual zombie is a far greater threat, however the spread should be far slower.