Why is quicksort better than mergesort?

Question

I was asked this question during an interview. They're both O(nlogn) and yet most people use Quicksort instead of Mergesort. Why is that?

Answer 1

On average, for average data sets Quick Sort's divide and conquer is faster than Merge Sort's divide and conquer. The difference is for Quick Sort much of the work is done during the divide step whereas in Merge Sort the work is done in the combine step. So while theoretically both their time complexity is O(nlogn), Quick Sort is faster in practice for most cases.

https://www.khanacademy.org/computing/computer-science/algorithms/quick-sort/a/overview-of-quicksort

https://www.khanacademy.org/computing/computer-science/algorithms/merge-sort/a/overview-of-merge-sort