Which one is better to use for actual product?

I’m wondering something about this post:


As a result of benchmark, the beginner solution is faster than the ES6 solution (I used this when solving the challenge) also the beginner solution is the fastest and the ES6 solution is the slowest.

When I read this post I am confused.
Which one is better to use when developing an actual product?
What is the important thing be faster or be shorter?

Challenge Link:

I created below code :
function largestOfFour(arr) {
let max=0;
const newArr=;
for(let i=0;i<arr.length;i++)
for(let j=0;j<arr[i].length;j++)
return newArr;

it works in https://www.w3schools.com/ , I don’t kown why it doese not work in this website.

If you have a question about a specific challenge as it relates to your written code for that challenge, just click the Ask for Help button located on the challenge. It will create a new topic with all code you have written and include a link to the challenge also. You will still be able to ask any questions in the post before submitting it to the forum.

Thank you.