Tag not monitored by Microsoft.
The both features are very different.
SQL Defender do what a Defender do: It protects your Azure SQL Database(s)
https://learn.microsoft.com/en-us/azure/defender-for-cloud/defender-for-sql-introduction
SQL Auditing tracks internal events
https://learn.microsoft.com/en-us/azure/azure-sql/database/auditing-overview?view=azuresql