Structured logging offers a variety of advantages, including simpler parsing, easier format conversion, and more flexible classification and correlation of events, even across diverse log sources.
About Structured Logging Each event is represented by an unrestricted set of key-value pairs
The BSD Syslog format provides only a very restricted set of metadata fields in the header. Any metadata that is specific to the event or log source, such as username or IP address, must be included in the free-form string.