Verdict

For a NAS or any RAID array, the HMS5C4040BLE640 is the clear pick - it's a CMR drive, while the DT02ABA400 uses SMR recording, which is not recommended for RAID. Only consider the DT02ABA400 for single-drive or archival use.

DT02ABA400 HMS5C4040BLE640
Capacity 4 TB 4 TB
Recording tech SMR CMR
RAID / NAS safe No Yes
Class Desktop Enterprise
Spindle speed 5400 RPM 5700 RPM
Cache 128 MB 64 MB
Noise (idle) - -
Fill Air Air
Interface SATA SATA
Failure rate (AFR) - 0.49%
Price / TB - -

Highlighted cells mark the stronger spec for a NAS build. Failure rates from Backblaze Drive Stats where available; $/TB shows once live prices are wired.