WD has introduced another part number for 6TB Purple. We already had WD60PURZ and WD62PURZ and now there is WD63PURZ

First of all , it is a CMR drive like WD60PURZ and WD62PURZ. The WD63PURZ has the largest cache (256 MB). The power consumption is lower on the WD63PURZ, probably because of the smaller number of platters.

Here is a table with a summary of the main differences.