I understand your question, that you want to know where Stacks is better than Arrays, as well as I read the comment of Jeanne as:
Jeanne Boyarsky wrote:They are different data structures. A stack is good for when you want to retrieve the last element added. An array is when you want to access any element at any time.
He is right, also I want to add some thing in his statement that size of stack is not limited while in array it is limited. And implementing a stack as an array is a bit more straightforward since we only need to keep track of the last element. We don't need to consider shunting items towards the head anymore, but we must still accommodate for new items which means we still waste memory allocating unused elements.