IIRC the distinction between db.*[hm] and db.*r doesn't matter on DW as everything's a dual-master setup.
But theoretically, if you will have issues with older data, don't use dbr/dbcr, and if you need the newest data or have to write, you must use dbh/dbcm

( dbr/dbcr would be the slave, dbh/dbcm would be the master )