Correct plural form of "hoof"

My research has shown that hoofs and hooves are correct plural forms of hoof. That being said, which is preferable? Which came first in the English language?

Solution 1:

The Old English word was hof; its plural hofas would have been pronounced with a v sound—[hoːvas]. Hoofs may be older by spelling, but hooves is probably the older pronunciation. This is backed up by the Middle English spellings houes and hooves, pronounced [hoːvəs]. So you can make an equally compelling case for each.

I like hooves, elves, dwarves, &c. but it’s a matter of personal preference.

Solution 2:

Well, as you can see in this NGram, hoofs is much older but has steadily been losing ground. Hooves seems to be the most common version today and has been for the past few decades:

The result is pretty much the same when comparing horse's hoofs to horse's hooves so it is not an issue of hoofs being used as a verb (as in he hoofs it). The pattern is also essentially the same for American and British English so it seems safe to assume that the variant hooves entered the language around the 1920s and has been gaining ground ever since.