2-factor authentication ensures an extra step of safety before you can login. It won't be possible for a third party to enter your account in case somebody got a hold of your password. The Google Authenticator is the safest 2-factor authentication method to use.
We recommend using the Google Authenticator over 2-factor authentication by e-mail as this is more subjective to fraud. Whenever a hacker or scammer has access to your e-mail, he will be able to log into your account. Whenever using the Google Authenicator, the hacker or scammer needs to have access to your phone ánd the Authenticator code which you carry on you.