If I created a Udemy account with my Gmail, then what’s the difference between signing in with email and signing in with Google? Thanks in advance.
In addition to allowing Google to manage the authentication process, signing in with Google allows Google to track your visits. In some cases they get additional data about content you view.
In many cases the mere presence of that button allows Google to track that your device visited the Udemy sign in/sign up page, even if you don’t click it. Google uses this to create and update a profile of you they sell for advertising and other purposes, and exposes you to more risk if your Google account is breached. With a password manager I find using SSO to be about the same level of effort as using my manager’s autofill functionality
One thing not mentioned is that if you ever want to “de-Google”, you will have to go to all websites and services where you logged in using your Google account, and (try and) change the authentication method. Avoid it if possible.
I had to literally recreate my Spotify account when I deleted Facebook, since there is just no way to login without it if you delete Facebook.
Adding on to this comment, it is very often not possible to change your auth method.
If you use email to register, you can almost always change to a different email (same method) but you can’t change between methods, like from Google auth to Apple auth, or even to a different google auth.
You’d need to create a new account, and therefore lose all the data on your old account.
Always choosing email gives you the most control and most privacy, I’d strongly recommend it.
Companies like google, facebook, and apple typically have better security. Other companies know that so rather than contracting with another third party or implementing themselves, they use oauth.
With oauth, apple, google, microsoft etc. will vouch for you. There are advantages and drawbacks, with, imo, the drawbacks outweighing the benefits. Key benefit being better security over poor practices and convenience. Drawbacks being less control of your accounts, consolidating your credentials into one basket, (especially if you use weak authorization), and the potential (likely) situation those accounts are monitored