Classic deployment vs. Resource manager deployment
I am working on setting up a web app which embeds PowerBI content. I am going through the steps to set up authentication with Azure AD and registration of the app, using several Microsoft docs. There are two ways to deploy the app, one being classic deployment and one being Resource Manager deployment. It appears that Resource Manager deployment is favored for new apps, as it is the more current technology. However, many of the instructions in the docs lead one to classic deployment pages.
What is the best way to register the app: Classic or Resource Manager?