I guess the question is whether you are using the hair for Catskill style split wings or for Usual (Comparadun) wings. In my experience, the hair closer or at the toes is longer and straighter and the hair at the heel is worn down, so shorter yet curlier.
The optimum hair IMO is from the 'instep' - long enough and curly enough for good floatation. I think, as with feather hackle, you have to look at the material and choose what looks best for the purpose. Whichever you choose, hold your cut selection by the tip (quite firmly) and brush out the underfur - this makes excellent dubbing.
Regardless of what part you choose, you will find the foot MUCH more usable if you first take a sharp knife (careful, don't cut yourself, the foot is tough), and slice the foot down from the top between the two main front toes. Then split the foot length wise. (Maybe use some work gloves - the bones splinter like chicken and can be sharp.) You will see the fur is much longer and easier to snip once you are looking at the 1/2 foot, and it is easier to determine what part is best for your needs.