During the fall in Nightfall, since he was unconscious, he was unable to compensate and his personal field went into survival mode - stopped at his skin - which also explains the suit burning off.
Maybe his entry angle was a factor too? When he flies fast, doesn't he angle himself to cut through the air like a dart, with hands straight out, maybe like he's diving, tiny splash? If he was unconscious, he would have been tumbling, right? wound up like a ball or a rock, big splash?
As far a vaporization, couldn't you take the density of some objects into account? say a block of iron as compared to a block of wood?
You got me thinking of the Phoenix affect in the 3rd X-men, how Wolverine's skin peeled off as he approached Jean Grey, but his adamantium skeleton remained solid against her "wind" of power.
