I believe the NC Tool hoof knife is the best value for the money.  They come sharp and are easy to keep sharp.  And they are relatively inexpensive to replace.  I think the best hoof knives in the market are Ringel knives.  I use them in my work, for they are made of high quality steel.  They are concave ground and will last for many years.  You have to sharpen them less than most knives.  They are solidly built and don’t come loose from the handles.  I like the custom made bone handles the best.  To save your knife, use a loop knife on the frog only.  You can use half-round nippers for dry frogs and soles to preserve your sharp knife.  I sharpen my knife occasionally with a chain saw file and dress them daily with a diamond hone.