What is the difference between the two ways of declaring variables in a for in statement?

if i use for in, i always use const to declare variable

const array = ["a","b","c"]

for (const value in array) {
  console.log(value);
}

but the other way is use global scope variable using let

let value
const array = ["a","b","c"]

for (value in array) {
  console.log(value);
}

the result is same, but i don’t know which way is better. Could you explain the difference between the above two methods in terms of memory or cost?

the result is same, but i don’t know which way is better. Could you explain the difference between the above two methods in terms of memory or other cost?