Verdict

These two are closely matched CMR NAS drives of the same capacity - decide on price and warranty. Check the live $/TB above.

MG09SCA18TE WD181KRYZ
Capacity 18 TB 18 TB
Recording tech CMR CMR
RAID / NAS safe Yes Yes
Class Enterprise Enterprise
Spindle speed 7200 RPM 7200 RPM
Cache 512 MB 512 MB
Noise (idle) 20 dB 20 dB
Fill Helium Helium
Interface SAS SATA
Failure rate (AFR) - -
Price / TB $35.67 $34.45

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.