Victoria Stillwell shared a link about reward based training (training based on giving or withholding a reward like a treat or praise) compared with aversive based training (training based on punishing undesirable behaviour with something unpleasant - like a yank on a neck chain - and encouraging desirable behaviour by releasing the pressure on the neck)...
which one is better for the dog's stress levels and the dog-owner bond?
Companion Animal Psychology: Dog Training, Animal Welfare, and the Human-Canine Relationship
I've been told often and long by some dog trainers who like to use all four quadrants in their training - which I respect for trainers with excellent mechanics and timing - but not for beginners or unco people like me...
that using tools like e-collar and prong collar has less stress (stress chemicals in the blood) than reward based training.
I think an inconsistent trainer is stressful for a dog - because it's harder for them to figure out what to do. But I'm sure we've all seen the depressed looking dogs with their heads down at some dog clubs vs the happy heads and tails up excited dogs that have been reward trained (praise, games, toys and food).