Horseshoes will be available at different levels and will enhance your horse's performance on various track types.
Higher level horseshoes will have a greater effect, but the effect will vary depending on your horse's base stats for performance on a particular track, or, in the case of training shoes, how 'trainable' they are.
However, a level 2 shoe will always provide a greater effect than a level 1 shoe and will degrade much quicker than a level 2 item. This means a level 1 item will need to be repaired and re-equipped more often.
Training shoes will add 6% to your horses trainability. This effect stacks with training increases from the saddles if they are both equipped.