Hi! I hear you: the amount of options out there are overwhelming, at times — especially when there is no one service that truly does everything you want it to.
The main reason someone might want to use Google Drive alongside Evernote is to use each service to their strengths — Evernote for notes and clippings, Google Drive for the general space to store anything and the full office suite for document creation.
If you just need something to store and tag documents, especially to have some notes attached to them, geotagging, and access to them on practically any device, then stick with Evernote. It’s a great way to keep an entire filing cabinet with awesome quick search capability right in your pocket.
If your workflow is more suited to traditional office apps and computer file folder structure, and the ability to work with, create, and edit most office type docs directly, use Google Drive.
Hope that helps!