I don't know if this will hurt or help but I'll wade in with this:
I learned this distinction thusly, and I welcome and ask for correction where I err. Our nature is neither inherently "good" nor "evil," as "good" and "evil" are personal attributes, not natural ones. Adam's nature was thus not ontologically different from ours, but it was illumined by the Divine Energies through communion with God. This was lost in the fall -- the illumined nature, not the "good" or "incorrupt" nature. This loss of the Divine Energies is what we would refer to as "corruption."
Christ restored the communion with God in His Person. In Him, the Divine Energies interpenetrated the human nature, and so in His Person, the nature was restored to a status of being illumined. We commune with Christ's illumined nature and thereby through Him, the communion with God is restored, and so we also are illumined.
As I understand it -- and again I welcome correction -- the nature is different in that it is illumined or not illumined depending on pre-fall, post-fall or post-incarnation. But the ontological properties of the nature itself did not change. That is how Christ could take on our human nature in all its "corruption" and yet not be considered sinful Himself. It is not Pelagian, far from it. Rather, it sets the ontology straight and avoids both the errors of Pelagius and Calvin.