On a more positive note, I have mentioned that long striding types have a superior edge, providing they have the speed.
Sometimes we aren't able to judge the stride for many reasons.
The horse may not be extended when parading, you may not be able to see the stride in a race because the horse is a bit obscured by other horses, or you may not be able to pick it up with the naked eye.
There is another way to pick stride without having to look at the gait.
If the vertebrae of the withers are long (front to back), the shoulder is more free to move backwards. This allows for an increase of stride length (and so it can increase the horse's speed). It is also important in jumping, as the shoulder must rotate back for the horse to make his forearm more parallel to the ground, which will then raise the animal's knees upward and get the lower legs out of the way. Therefore, the withers have a direct impact on one of the most important points of conformation: the shoulder.
It is not necessarily the height of the withers, it is the length of the withers.
These are the horse's withers:
When going to look at suitable horses for dressage, eventing, jumping and even potential breeding or those suitable to race, I always look at the combination of withers and stride if I can.
Short withers are really bad, but ssometimes you can pick up a bargain if the horse has short withers, poor stride but has grand sire and dam with very good withers. This would be a case where I would purchase the horse for breeding at a fraction of the cost. Of course they may breed several short withered horses depending on the dominance of the gene.
Mixing various sires and dams can sometimes get a long withered horse, with good bloodlines and this is the cheapest way to get a very good horse.
If you look at all the champion sires, and racehorses, they usually have a combination of high and long withers, very prominent.
My horse Chrome Prince, which I owned a very long time ago, was a sprinter but had very short withers. He was a gelding and was not fast enough to make the grade, but did win a lot of picnic races because he had one burst of speed. He was well muscled and had a very good chest, but didn't have the stride or the withers.
Here are some pictures of some very good horses, note the actual wither definition. This is a key part of conformation.
Note the actual wither definition, the rise from the neck and the length, they all have this in common, and one could make informed decisions without seeing the stride at all. However, of course it's most preferable to see the combination of withers, stride and gait.