Imo, the main point of a system like log4j or slf4j if the ability to have logging in your service up to the point of it being a massive performance impact - and keep it disabled.
For example, Hibernate has full query logging built in, but even if you filter locally with some logging demon, pushing 100 - 1k queries / second to stdout or a file is going to cripple performance.
With a logging framework like Log4J or SLF4J you can have this query logging, and you can enable it within 1 monitor run (usually 60s) at runtine and disable it 4-5 minutes later. This is very, very powerful in production.
Please not filebeat. For a few months I had this recurring problem where an app was logging way too much stuff. Filebeat dutifully accepted it and then created ghost files as a buffer which then filled up the disk and crashed the app.
Depending on the velocity at which the log barf was being produced, we sometimes had a short window in which we could manually (!) log in via SSH (!) and restart filebeat to force it to close the open file handles at the cost of losing everything being buffered locally (!).
