"null elements are allowed in the LinkedList implementation but not in the ArrayDeque implementation.
In terms of efficiency, ArrayDeque is more efficient than the LinkedList for add and remove operation at both ends. The best operation in a LinkedList implementation is removing the current element during the iteration. LinkedList implementations are not ideal structures to iterate.
The LinkedList implementation consumes more memory than the ArrayDeque implementation." - As specified in the ultimate source of truth.
So if you don't have to support NULL elements && looking for less memory && efficiency of add/remove elements at both ends, ArrayDeque is the best choice!!!