Verdict

Both are comparable SSDs. The WDS400T1R0C is rated for more write endurance than the MZ-V9P4T0, so it's the longer-lasting choice for a NAS that sees steady writes; for light use either is fine and price decides.

MZ-V9P4T0 WDS400T1R0C
Capacity 4 TB 4 TB
Form factor M.2 M.2
Interface NVMe NVMe
NAND type TLC TLC
Endurance (TBW) 2,400 TB 5,100 TB
DWPD - 0.7
DRAM cache Yes Yes
Power-loss protection No No
Sustained write - -
Price / TB $156.33 $253.68

Highlighted cells mark the stronger spec for a NAS build. Failure rates from Backblaze Drive Stats where available; $/TB uses the cheapest live price where available.