Is Rahr 6-row and Briess 6-row the same thing with a different company name. Or is it something completely different, with different flavors and color?
Different maltsters - Briess is out of Chilton Wisconsin and Rahr is out of Minnesota. Are the grains the same? Who knows on the supply chain, but they are probably pretty similar given their locations and likely farm suppliers.
there will be differences related to process at the malt house but they should have simliar characteristics. in the same way that weyermann pils and best pils will be different but both identifiable as pils malt.
They are not going to be identical, but they will be similar and probably have only subtle flavor differences. They can certainly be substituted for one another unless you really like a particular characteristic of one.