Natural Balance Shoes are meant to bring the breakover back, to lessen stress on tendons, ligaments and for treating Navicular syndrome, etc. Breakover is the point in the stride in which the hoof begins to leave the ground. A longer breakover can be caused from a flat shoe, or unbeveled hoof wall, or excess toe left on the hoof. This stresses tendons as they have to work harder to get the foot off the ground, and increases pressure on internal anatomy, and often will cause the hoof wall to "flare" which is much like making your fingernail bend backwards, as the hoof tries to get rid of excess length.
The special shoes can really help horses that have long toes or already have navicular syndrome or other lameness issues associated with a long breakover (though since I am a barefoot trimmer, I say you can get better results with NO shoes at all, but these are a step in the right direction). The fault I have with them, besides the fact they are shoes, is that the breakover is only changed in the front of the hoof, yet horses turn corners, not just walk straight lines, so the breakover should be brought back on the front quarters as well. Square toes tend to get toe cracks, as the hoof is not a square structure to begin with, and landing on uneven ground tends to cause a shearing type force that splits the wall, and horses that make fast turns are usually the first to show it.
Going barefoot with the bevel all the way around the hoof, allows for faster breakover all around, eliminates the toe cracks, and the hoof gets better circulation without ANY shoes of any kind, but if you are going to insist your horse has shoes, a modified shoe with a bevel all the way around the front quarters and toe, will at least alleviate the breakover problems of shoeing. The hoof is still going to get inferior circulation from being elevated by the shoe. The frog and heel area should always land first in the stride for maximum shock absorbtion and proper mechanics, but with a shoe, it's hard to get the frog to get proper stimulation. Pads can be added, but they will often just seal the frog off and breed thrush, which softens and weakens the frog, making it tender, so the horse will tippy toe anyways.
Any kind of Bar shoe is designed to stimulate and support the frog and heel area, but really just make the structure weaker. Flexiblity is vital, metal doesn't provide that, and constant pressure further compromises circulation. They need pressure/release from the motion. Consider this, if someone massages your toe, with a pressure/release, it increases circulation, but if you put a rubber band around it for "constant stimulation" it would actually slow or stop blood flow. Again, the best thing I've seen is a good barefoot trim for hoof health.