These drives support the ATA Streaming command set in addition to the regular ATA commands that are supported by desktop drives. DVR applications need to record the file system metadata with the same integrity as desktop drives (using regular ATA reads and writes), but they are allowed, by the DVR's firmware or operating system, to drop frames when reading video files (using ATA streaming commands). That's the only significant difference.Normally I would chose the CMR one (WD43PURZ), but WD43PURZ is marketed as a surveillance drive (and some bad sectors on such drives is not seen as a big deal).
both WD40EZAX and MD04ACA400 are at the same price range, which should I prefer?WD40EZAZ is SMR.
The WD Blue 4TB CMR variants are WD40EZRZ (64MB cache) and WD40EZAX (256MB cache).
Toshiba MD04ACA400 seems to be a CMR drive.