Give your opinion, whether you agree or not.

1. The main difference between a Windows Authentication and an SQL Server Authentication is that accounts are authenticated by Windows Authentication when the account is present in the Active Directory for the Domain. This is opposed to the way that SQL servers authenticate users, which is by checking if the account is active and then if the password that the user enters works. Windows authentication all happens in the Domain active directory, whereas SQL server authentication is done from the SQL server's master database.

2. When a user attempts to connect to the SQL Server from a nontrusted connection using a specified logon name and password, the SQL server first performs Authentication by looking to see whether or not the user attempting to connect to the server has a login account that is saved in its database. If the user is in the database, the SQL Server will then check if the password matches the one that is attached to the account in the database. If it doesn't match, the connection will fail. Users should never be able to connect to an SQL Server platform from a nontrusted connection, it should only be done by administrative users and only over a secure trusted connection. 

3. The reason that it is not advisable to enable the SA account in SQL Server is because the SA account comes by default with very high levels of access. In addition to that, the account has been known to have certain vulnerabilities attached to it, such as being able to change the login credentials of the SA account and then use that account to carry out malicious actions. The SA account should be disabled.