OOP is better orienation because you only use what you need. OOP is like bunch of wardrobes with drawers and when you need something just go and pickup what you need. From server side, in OOP , server pickup only class names and keep them in own memory. When you open that class, server only then start to indexing and looking objects (functions, variables, etc.) inside that class. If you work ony with functions (not OOP), server indexing all functions what you have and you waste more memory on "junks". Also OOP is code-less aproach if you learn how to handle with objects.
Advantage of OOP is also modular approach. You can always extends your functions, easy find error or use any object anywhere. Also you can give permission for each function (object) inside class and decide what is public, protected or private.
Best approach to learn OOP is that if you know made functions, just simply classify that functions inside one or few class, call class and it's functions where you need. Is simple approach and you will start to learn orientations. Next approach is to give permissions to that functions. Next approch is to use functions inside functions, collect one algorythm what you have inside many functions, place in one private function and include like object where you need etc. Learn slowly and wise.