It is one thing to have a big KO percentage against cruiserweights, it is another to have it against heavyweights. Whoever has any doubts check out Juan Carlos Gomez record. He stopped almost everyone at cruiserweight but at heavyweight I do not remember him KOing anyone major. It does not mean the same will happen with Haye but it could. So the time will tell. It is just speculations at this point.
I know its only sparring, but its been reported Haye sparked Arreola, so I have a strong feeling his power will carry.
of course he doesn't punch harder than wlad. haye has got a pretty good right hand himself but wlad has stopped credible opponents with single shots and when he goes for the kill with combinations like in the mercer or byrd fights you can see how overwhelming he is physically.