Did you know that dogs trained by different styles/methods have different "looks?" It's true! Often you can get quite a bit of information on how the dog was trained just by watching a short obedience segment -- maybe sit, down, stay, heel and come when called.
Dogs who were trained with heavy-handed, punishment-based techniques tend to complete the obedience pattern slowly with their heads and tails down. They are usually accurate, but slow. They look relieved rather than happy to receive praise for having gotten the behavior correct. Even if the dog is successfully trained -- gets the obedience routine 100% and you do not observe the owner correcting or punishing the dog, this slow-mo, underwater quality to the movements usually cue you in that this is not particularly fun for the dog and may also be a little stressful.
Dogs who were trained with positive, motivation-based techniques will usually be a little sharper, a little quicker, and a lot happier and more bright-eyed. During the training process they were not punished for making errors, so they are confident to move out well and complete behaviors faster. A waving or wagging tail is a hallmark of a dog trained with reward-based training; they have internalized the understanding that training and obeying is good and fun! Even if you do not witness the owner giving any treats or toys to the dog for a correct obedience behavior, you can still usually tell that the dog was trained with this method!
You have to wean a dog off punishment-based training methods (jerking, spraying etc) just as much as you have to wean them off of reward-based methods (treats, toys.) At the end of the day, when the dog has been weaned off of whatever training tool you have used, and all other things are equal -- which "look" would you rather have for your dog?
I thought so!