I can only speak to the black walnut species, as I have not worked the others, but I feel as though I have a unique insight to give. Running our own sawmill as a side business we very rarely saw a log that we did not cut from the tree ourselves; meaning I see beforehand the tree where and how it grew before it ended up on our mill. I have noticed the largest quality difference in walnut depends on where it is grown. A creek bottom walnut that was shaded out for most of its first thirty or so years and has had to compete with oaks, hickorys, sycamores and others throughout it lifetime has growth rings that are much closer together and more densely formed that one that was grown in the edge of a field or even in an openly spaced grove. Slow wood is strong wood. I know most people do not have the luxury of seeing where the wood was grown, but it does make a difference in the quality of the wood. This appears to be true for most all wood species, at least the ones I have come across.