If The Shoe Fits Wear It

In the major scheme of things if the shoe-size fits wear it. The main concern when shoeing a horse is not particularly the size of the shoe, but properly trimming the foot then putting a shoe on that fits from the toe (or the desired breakover point) all the way to the heel buttress.
I think for many years some horse breeds wanted small hooves for a nicer look. And possibly various lameness arose from actually forcing the hoof to become small in appearance. Now, I believe the pendulum has swung in the opposite direction and people are determined to have the shoer put the biggest size shoe possible on the horse. When in reality a good shoe job, one that not only looks nice, but also promotes the wellness of the horse from a hoof standpoint (no pun intended!!) is no better than the trim.
Horseshoe manufacturers have unlimited types of shoes for the farrier to choose from. Which correlates with much discrepancy when sizing a shoe. Typically, the smaller the number the smaller the shoe and the more 0’s the smaller. i.e. 000 is smaller than 00 which is smaller than 0 which is smaller than a size 1. Sometimes a different style of shoe from the same company will have a different sizing number, yet in actuality be the same exact size. Thus, just from this reality it is important not to get hung up over the size of shoe your farrier is nailing on your horse.
I have had a number of horses in my clientele base over the years that I have actually shod with one size at one appointment and the next appointment ended up going to a bigger or smaller size. I don’t know if that is technically correct by others in my profession, but the truth is the truth. Each time I just tried to prepare the hooves correctly for that horse at that time and fit a shoe to my trim. Sometimes, if I have a horse that habitually loses a shoe I will try and evaluate my trim/angle/balance and by getting that correct I will end up putting a different shoe size on that doesn’t get pulled...sometimes it turns out to be a bigger size and sometimes a smaller. Other times the size difference comes about after working on neglected feet, a lame horse, or a change in the use of the horse by the rider.
If the shoe fits, stays on, doesn’t cause lameness, looks good, aids in performance --- wear it.