MySQL vs. MariaDB Binary Logging Difference
There are many differences in default values for system variables between MariaDB 10.3 and MySQL 5.7, so that can explain both some of the performance and binlog size differences. Additionally, MariaDB 10.3 is of course newer code, being the most recent major MariaDB release at the moment, whereas MySQL 5.7 is not the most recent MySQL major version since the release of 8.0.

For example, the default value for binlog_format is different between MySQL 5.7: ROW and MariaDB 10.3: MIXED. MIXED means statement-based in most cases, and statement-based binlog format has the advantage of less data written to log files:


  When updates or deletes affect many
  rows, this results in much less storage space required for log files.
  This also means that taking and restoring from backups can be
  accomplished more quickly.


MariaDB also has log_bin_compress, see Compressing Events to Reduce Size of the Binary Log, though this is disabled by default.