Short crest release: the rider slides the hands up the crest as the horse takes off, not before (which "drops" the horse). The hands should not slide far up the crest, only a couple inches, as needed. It provides support for the rider's upper body, while still providing a good amount of control because the rider did not release any more than needed. Best used on verticals, when the rider needs to turn mid-air, or when going down drop fences. An intermediate release.
Long crest release: Similar to the short crest release, in that the rider slides his hands up the crest, but the hands are pushed much further along the neck. Gives a great deal of freedom, but fairly little control. Best for very wide oxers, to allow the horse to really stretch across, or for green horses that may jump large or awkwardly, for gymnastics grids, and for use on horses that have been hit in the mouth over fences and are reluctant to jump or stretch down over a fence. The rider should be careful not to associate a large movement forward with the hands and elbows to mean a movement forward with the hips. The hip angle should still close backward. Many riders get into the habit of jumping ahead with this release. Critics say this release is overused and exaggerated by hunter riders; in the hunter ring it is often used by experienced and/or professional riders on well-trained horses over jumps of relatively modest size. Proponents say that this shows off a talented hunter by proving the horse needs little assistance from the rider to jump in good form.
Automatic release: The most advanced release, where the rider maintains a soft, elastic, steady rein contact with a straight line from elbow to bit as the horse jumps. This release results in a great deal of control and communication between horse and rider, allowing the rider to signal to the horse what to do on landing. It allows the rider to better turn while in the air, to correct horses that jump crookedly, and to provide the support that some horses prefer over fences. It is also good on horses that need lots of control after landing. However, the automatic release requires perfect balance from the rider to be executed correctly. An unsteady rider will catch the horse in the mouth, and an incorrect automatic release will spoil a horse's jump and confidence. However, if a rider is able to perform it correctly, it is often best to use this release whenever possible. Very useful in show jumping and eventing, where control is very important.
I don't teach ANY release that has people pressing their hands into the top of the horse's neck. If the horse were to need some rein, the rider would be unable to give it, since they are on top of the crest and locked in. Also, pressing onto the top of the crest encourages the rider to go too far forward with their upper body and "prop up" their upper body, instead of using their lower leg to counterbalance the weight of the upper body. I teach a "crest" release that has the rider pressing the hands onto the sides of the crest instead of the top of the crest. That way, the hand is able to give some rein to the horse, if needed.
I will use myself as the example of the releases I prefer. BTW, my lower leg is further back, here, than I like. I am riding very aggressively for time and I sometimes get a little sloppy. Oh, well...
This is the "crest" release I teach;
Notice the hands are on the side of the neck. It is not an auto release, due to the broken line from the elbow to the bit.
The auto release is what I want all my riders to try to attain. Some jumps, especially when going XC or riding for time, just are not where you would use the auto release. This is where there is a straight line from elbow to bit. This allows the BEST feel of the horse's mouth and allows the rider to adjust the reins as needed. This is an auto release;
My critique here is my hands are too open, not gripping strongly. This can allow rein slippage. Again, oh, well...
Well, I think it is more about how I was riding in those photos. The first one I was riding for time and therefore very aggressively. Also, look at the angle of the horse. The first photo the horse is at a steeper angle in relation to me. To flow with the horse, I have to take HIS angle into account.
The second photo is a first round photo. I am jumping much more carefully. Time is not as big an issue than if I incurred any faults. Then I wouldn't get a second round for time. Also, his angle is much shallower relative to me, so I don't look as low.
So, a good thing? Hmmm....it is more whatever it takes to flow enough with the horse so that you don't interfere with him. I am not an "equitation" rider so don't claim to have pretty form. I believe pretty is as pretty does.