Originally Posted by Bobby Fischer

It comes down to the individual horses.
Take a horse like Hard Spun for example. He isn't really a sprinter. His strength is his high cruising speed and his pedigree. He can breeze faster than this others and for most of the race. When asked to go slower for the whole race he doesn't benefit any positional advantage from his cruising speed, he doesn't really save that much more energy, and he doesn't have turn of foot to kick home fast.

Now a slow pace would on the other hand help a sprinter type. It would generally hurt a closer. When everyone is within a few lengths and no one has momentum, it is all about position and turn of foot.