Each Breed of horse has a different temperment and way of moving which we must understand in "seeing what we are looking at"

The piaffe is a dressage movement where the horse is in a highly collected and cadenced trot, in place or nearly in place. The center of gravity of the horse should be more towards the hind end, with the hindquarters slightly lowered and great bending of the joints in the hind legs. The front end of the horse is highly mobile, free, and light, with great flexion in the joints of the front legs, and the horse remains light in the hand. The horse should retain a clear and even rhythm, show great impulsion, and ideally should have a moment of suspension between the foot falls. As in all dressage, the horse should perform in a calm manner and remain on the bit with a round back.

The piaffe should be straight and come from the rider containing the horse's great desire to go forward.
The horse should lower his hindquarters, collect, and raise his shoulders by taking weight onto his hindquarters, rather than hollowing his back and piaffing with his hindquarters trailing out behind him.
Bending of the joints is not always a good indication of true collection (and therefore a correct piaffe). It is possible to perform a piaffe-like movement with good bend in the legs while the horse remains hollow and on-the-forehand. This can especially be seen in horses trained to trot in place by holding them back while asking the hindlegs to bend by applying the whip on the hocks.
The horse will bend his hocks, but will not lower his hindquarters.
The horse should not piaffe higher with his hind end, which comes when the horse is on the forehand, nor should he have exaggerated bending of the front legs without true collection.
The horse should remain relaxed and supple. He should not piaffe with short, jerky steps.
The horse should remain straight, rather than piaffing with his legs moving out to the side or crossing.
The horse should not move his fore legs backwards toward his hind legs, so that they are more under his body, but rather keep them perpendicular to the ground.
The horse should remain at or in front of the vertical , with his poll as the highest point.
The horse should maintain the rhythm of the trot.

Above is what is know as a defined standard. I helps you to judge/decide if something is being done as correctly as it is defined. It is what gives the edge to equally skilled trainers in a "competition" It is difficult to speculate on because it is crystal clear, and it doesn't allow a lot of room for opinion, other then how close the animal/trainer came to perfect or a standard. Without it "who is better/who is the winner" is only that. An opinion, based on many emotional/social factors, with the animal often not being considered an given the short end of the abuse stick.