CodeIgnitor vs row PHP

Codeigniter, or any other framework, serves the purpose of preventing you from having to recreate the wheel. Very important functionality that is necessary in practically every app is already made and tested for you.

Raw php is quicker, but if you're not a very experienced coder, also leaves the chance of you making some pretty bad mistakes when writing code.

The performance hit you take by using a framework is negligible compared to the benefits it gives you

Codeigniter is simply one of the tools you need to learn to be a successful developer. Always add more tools to your coding arsenal!