[HerenIstarion]

The difference being, Gandalf (as opposed to time when he was Olorin) is 'truly' incarnate, not 'clothed', i.e. while clothed Valar and Maiar may eat not, and suffer not the hunger, Gandalf, incarnate into real flash, would starve. He was not able to drop his visible form at will, nor assume it again at will. He was truly slain and resurrected into the same form, and, I believe, not because of what he was, but because the body left on the site was the same. The changed status of indwelling spirit made it more powerful.

As for the changed status - the whole affair is reminiscent of Christ conquering death (even the timing in between his death and resurrection)