[Plugin: Google Analytics for WordPress] Why should I use this plugin?

No reasons for or against this plugin? I need help figuring out if I really need this or not.

Perhaps you need to ask yourself how you use analytics and what you want to get out of it. Then go to https://yoast.com/wordpress/google-analytics/ to understand what this plugin can do and how to configure it.

If you already have Analytics installed there is no point in using it. The point is if you don’t want to manually install the code, this plugin puts your tracking id on every page (plus it has some advanced tracking features, or makes them easier at least).