Objectively, his only strength is he can sometimes score goals other strikers can't. Sometimes.
Otherwise if you're honest, you would prefer Milik for passing, hold up and aerials and you'd prefer Kean for pace, dribbling, strength and probably movement.
His effectiveness relies solely on him scoring bangers because in a year i haven't seen him do much else. He hit a wicked switch last match but it happens once a month. His head is otherwise completely down at all times