I have eaten at them all, but we don't have a KFC restaurant in Bologna. Burger King is my personal pick. The Whopper is a good sandwich. McDonalds is the most popular in Italy, so I eat there sometimes with friends.
My favourite burger fast food place is either A&W or Harveys, and my favourite chicken place is Popeyes. If Swiss Chalet counts as fast-service food, that would be top. None of those are available where I live, so the craving this post has created will have to go unfulfilled.