The ring you clip to changes the physics of the walk more than the harness brand does, and most of the frustration people have with harnesses comes from using the wrong one for the dog in front of them.
What a back clip does
Clipped between the shoulder blades, forward pressure travels straight down the lead. The dog leans into it, and leaning into a harness is exactly what sled dogs are trained to do. For a dog who already walks on a loose lead, this is the comfortable, low-interference choice. For a puller, it is an amplifier.
What a front clip does
Clipped at the sternum, forward pressure rotates the shoulders back towards you. The dog turns sideways instead of accelerating, so pulling stops producing forward motion and stops paying. It is not a correction and it does not hurt; it simply removes the reward.
When the front clip is the wrong answer
On a dog who does not pull, a front clip does nothing useful and the lead tends to swing across the front legs. On a very small dog, the lead can tangle under the chest. And a front clip is a management tool, not training - it makes the walk possible while you teach the loose lead, rather than replacing that work.
Why ours carry both
Dogs change. A puller at eight months is often steady at two years, and a harness with both rings covers the whole of that without buying twice.