The worst-case running time of the merge sort algorithm is better than that of the quick sort algorithm, if the pivots are chosen arbitrarily code example

Example: merge sort vs quicksort

Efficiency :

Merge sort is more efficient and works faster than quick sort in case of larger array size or datasets.
whereas
Quick sort is more efficient and works faster than merge sort in case of smaller array size or datasets.
Preferred for :

Quick sort is preferred for arrays.
whereas
Merge sort is preferred for linked lists.