The best of dogs will fill up the country and cover the ground...so you don't have to. The best of dogs will dial it down when the cover gets thick and the terrain gets lumpy and dial it up when the terrain flattens out and opens up.
Some folks are uncomfortable with a dog that goes out of their sight. Some are not. It depends.
The difference between and 800 yard dog and a 100 yard dog is often the country it is hunted in, and that is how it should be. The dog that ALWAYS hunts at 100-200 yards, no matter when, no matter where might be what some are looking for, but it is a dog that has limited potential. The dog that dials it up and dials it down, a dictated by the terrain, and/or the desire of its handler/hunter is the dog with greater potential, IMO. Such a dog might take a little more to get them to where you need them to be, but, speaking for myself...it is worth the extra effort.
I have dogs that I can run in front of a horse at a field trial and be competitive. I can take those SAME dogs, put them in a 40-50 acre preserve field and kill a dozen pheasants over points. I ALWAYS hunt my field trial dogs. It makes them better dogs, and I like to kill birds over them. Some are better at the switchover than others, but they all get it eventually.
FWIW, many cover dog pointers trace back to Gunsmoke breeding, which was Horseback open shooting dog breeding. Take those dogs out of the woods and many of them will scorch the ground if you want them to. I know, because I had some of them. They were bird dogs.
The real difference is: Are they running to hunt, or are they running to hear the wind rush through their ears? The best of them run AND hunt for you.