The end result is a more stable new installation of SQL Server.
With a clean upgrade, the database also can remain available on the original system while you perform the install on a new one.
Be aware that you cannot change the features to be upgraded, and you cannot add features during the upgrade operation.
For more information about how to add features to an upgraded instance of SQL Server 2017 after the upgrade operation is complete, see Add Features to an Instance of SQL Server 2016 (Setup).
There are two basic strategies for upgrading to the new release: Each method has its advantages and disadvantages.