In addition to what evanelias said, a logical dump also means we can load it into a MySQL instance running a different storage engine as well. In our case, it allows us to take a mysqldump from an InnoDB instance and load it into a MyRocks instance if we wish.
Yes, logical backups are smaller due to lack of index overhead. And since logical backups are textual, they can also be used for other clever purposes, such as ETL pipelines.