But do you know what isn’t subjective? Your dog’s health. Collars can cause injuries. When a leash pulls back on a collar, there are blood vessels being constricted, pressure on the thyroid gland, potential deforming of the base of the tongue, and possibly even nerve damage. A leash is not a steering mechanism. Yanking and leash-snapping only result in more yanking and leash-snapping.
The problem is that, all too often, a leash function as a steering mechanism, whether it’s the dog attempting to steer the human by pulling, or the human attempting to pull the dog along or back. In an ideal world, that pulling action wouldn’t happen. But since it does happen, it’s better than the force is spread over the dog’s body through a harness rather than concentrated entirely on the neck with a collar.
But don’t harnesses encourage pulling? There’s a persistent (but inaccurate) belief that, because of their inherent opposition reflex, harnesses encourage dogs to pull against the leash as they lean into the harness, kind of like sled dogs do. That’s always been a mistake of confusing correlation with causation. A dog who wants to pull is going to do so whether they’re wearing a collar or a harness. The difference is that harnesses don’t have a high risk of causing injury during pulling.