Delete in this case will only set the element as undefined:
> myArray =['a','b','c','d']
>delete myArray[0]
true
> myArray
[undefined,"b","c","d"]
Splice actually removes the element from the array:
> myArray =['a','b','c','d']
>myArray.splice(0,1)
true
> myArray
["b","c","d"]