The difference would be converting all the places in your code from strlen($string) to $string->length() instead of rewriting it. One may take a few days/weeks

The difference would be converting all the places in your code from strlen($string) to $string->length() instead of rewriting it. One may take a few days/weeks to do in an existing app. The other would take months if not years to get out the door, test, and deploy.