Technical difference between Locked and Unlocked maps?

Most maps found here under new maps contain locked and unlocked versions of it. As I believe it's easy to use the Unlocked version straight away. But, is there an advantage of using a Locked version of the map? I red in a forum that Locked version has more features.. Please confirm the advantage of using a Locked version over an Unlocked one. - Cheers!

I have a Kenwood DNX7200 system. The kenwood does not support unlocked maps, hwever standard Garmin locked maps with .UNL file are supported.