By keeping a foot on top of the ground instead of in it, we can reduce the amount of effort the horse expends, therefore making the horse a prettier mover. Flotation can also be used on one side of the shoe to help balance a foot that carries more weight on one branch than on the other. The width of the shoe must be measured on the ground surface not the foot surface. If a shoe is sharply tapered to improve traction, it will allow a foot to go deeper into the arena and also make it stick. Neither will do much to improve the way a horse moves.
Flotation is also very important on the hind feet.
If you expect a horse to carry more weight on the hind quarters and lope deeper, give the foot the ability to do that with a wide-web aluminum shoe behind. I saved one very important aspect of aluminum for last because it is a very important benefit, but the least understood. Simply put, it is wear . As a foot grows, the toe gets longer and the angle of the foot tends to lower. These two actions delay the breakover of the foot, changing the way the horse moves and putting strain on the suspensory system.