I have a web app where I need to change a drop down list dynamically depending on another drop down list. I have two options: Get all the data beforehand with PHP and "manage" it later with Javascript. Or get the data the user wants through AJAX. The thing is, that the page loads with all the data by default and the user can later select a sub category to narrow the drop downs. Which of the two options are better (faster, less resource intensive)?