Verdict

For a NAS or any RAID array, the ST3000VN006 is the clear pick - it's a CMR drive, while the WD30EFAX uses SMR recording, which is not recommended for RAID. Only consider the WD30EFAX for single-drive or archival use.

ST3000VN006 WD30EFAX
Capacity 3 TB 3 TB
Recording tech CMR SMR
RAID / NAS safe Yes No
Class NAS NAS
Spindle speed 5400 RPM 5400 RPM
Cache 256 MB 256 MB
Noise (idle) - 23 dB
Fill Air Air
Interface SATA SATA
Failure rate (AFR) - -
Price / TB $61.13 $55.80

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.