I don't consider Chiellini as that "super talented defender" that guys in this forum think he is. He's great in the air (probably among the best in that "aerial Dep"). Great strength and great at man marking "big attackers" but lacks the quality that i consider the most important part in any great defender and that is confidence.
The guy panics whenever attackers get close to him and it shows. He doesn't have that cool head and confidence that almost all the really talented defenders have. Plus He seriously struggles when faced with pacey attackers specially on the counter.
Like I've said i don't expect guys here to agree with me on this.
I know what you are saying in terms of style, but I don't see how you can compare their standing given the level that Chiellini has played at for Juventus and Italy as a starter, and Ranocchia who has had one half of an outstanding season. If you are talking about potential then fair enough.
BTW I don't think Chiellini struggles with pace either, he is not a slowish battler like John Terry or Nemanja Vidic who have to defend with the ball in front of them, but then they have not played in the wider areas he has as well. Chiellini isn't exactly Nesta or Cannavaro in their prime fast but he does get back to make challenges. Lets face it, any defender can struggle against pace, especially if they get the wrong side.