Nearly everyone will find that it is best to stick with the default settings and use the superglobals - not only is it the recommended way, but it is also the most secure, and will guarantee your code will work on other machines without the need to edit the php.ini file.
Nevertheless, it is important to have a good understanding of what other code is out there in the wild - there are usually several methods to accomplish the same task in PHP, so you should be ready for anything!