Verdict

Both are comparable SSDs. The MTFDKCC3T2TFS is rated for more write endurance than the KCD8XRUG3T84, so it's the longer-lasting choice for a NAS that sees steady writes; for light use either is fine and price decides.

KCD8XRUG3T84 MTFDKCC3T2TFS
Capacity 3.84 TB 3.2 TB
Form factor U.2 U.3
Interface NVMe NVMe
NAND type TLC TLC
Endurance (TBW) 7,008 TB 17,500 TB
DWPD 1.0 3.0
DRAM cache Yes Yes
Power-loss protection Yes Yes
Sustained write 3,800 MB/s 5,000 MB/s
Price / TB $265.11 $637.19

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.