My dogs are off leash the vast majority of the time. We do a lot of hiking in the summer and skiing or snowshoeing in the winter. Some of the trails that we go on are steep, rocky or narrow or all three. I feel more secure not having to hold onto a dog while I negotiate a tough trail. The same applies to skiing or snowshoeing in tougher terrain. I am not coordinated enough to skijor. So I don't want the dog attached to me if I have to concentrate on a steep area or a weird traverse. It's safer for the dogs as well as for me.
If we're just walking on the road, the dogs are leashed. I have nothing against leashes.
I love this best with Dakota. She can run free but still keeps close enough to me so I can see. She has seen other cars, machines, and people, and so far she doesn't care but we have yet to let her off leash when we spot a dog and we have spotted the dog before she did which was good cause we don't know how distracted she would be off leash with another animal like a dog, a rabbit etc...
I'm not sure exactly what you're asking for. When I train my dogs 9 times out of 10 they're off leash because it frees my hands up. We'll be in my fenced in yard or inside at the time though. I would personally never, ever, ever, ever, ever let my dog off leash in an unconfined area. I don't trust other dogs and I don't trust other people. I don't think I could ever be completely positive that ten times out of ten the dog would stick by my side.