Don't feed a hoof supplement, but to use Cut Heal Hoof Heal, and it works great for me; the feet stay hardy, moisturized, and it also helps prevent thrush.
I am not normally the kind of person who likes an 'outside' remedy, either, but I started using it back in 2006, on a gelding with really dry, cracked and easily chipped feet, and it gave him such good feet, I have used it since on all my horses.
For an internal supplement, I have used Farrier's Secret, and liked it as well, but the smell is too powerful for some horses, and they won't eat it!
As feet are a part of the body and as there are no 'ingredients' that are required specifically by the feet, good, balanced nutrition for the whole horse is the best IMO. I personally feed a 'ration balancer' for this, after analysis. FeedXL.com is a very good service/program IMO & it is what I subscribe to & personally recommend with regard to balancing diets.
Biotin is indeed one of the many ingredients needed for health(of all sorts, not just hooves) that *may* be deficient in the diet. However, if the horse is getting adequate green forage - eg grass, lucerne, etc - they *should* be getting enough in their diet without supping. If the horse isn't actually deficient(& apparently biotin deficiency is rare) it will not help improve anything. But at least, unlike many nutrients, it is apparently not harmful when over supplied, just excreted, wasted. I can forward an article on the subject, from the nutritionist at FeedXL.com if you like.