Both are great materials for your sub-base

CMB is a blend of recycled concrete and/or recycled asphalt and consists of a sand-gravel mixture of varying-sized particles up to ¾ of an inch in size. Decomposed granite, or DG, is granite rock that has weathered to the point that it readily fractures into smaller pieces of weak rock and/or into mixtures of gravel, sand, and silt-size particles of clay. Both are great materials for your sub-base. CMB is more easily compacted than DG but doesn’t drain quite as well. DG, meanwhile, yields a smoother finish than CMB but it is quite a bit more expensive. Generally, CMB is the best choice for artificial grass in landscaping while DG is the best choice if you’re installing a putting green.