splice() modifies the original array while others create new arrays: 1) splice() can add or remove elements at any position, 2) map() creates a new array with transformed elements, 3) filter() creates a new array with filtered elements, 4) slice() creates a new array with extracted elements, 5) Understanding which methods mutate arrays is crucial for predictable code, 6) Mutating methods should be used carefully in functional programming, 7) Non-mutating methods are preferred for maintaining immutability, 8) Helps prevent unintended side effects in larger applications.