Verdict

These are comparable SSDs. The WDS400T1R0C is rated for the most write endurance, so it lasts longest in a NAS that sees steady writes; for light use any is fine and price decides.

WDS400T1R0C
WD Red SN700 · 4TB · NAS
$1,443 ($360.75/TB)
WDS400T2X0E
WD Black SN850X · 4TB · Desktop
$790 ($197.50/TB)

Value at a glance

Price / TB
WDS400T1R0C $237.20
WDS400T2X0E $197.50
Endurance (TBW)
WDS400T1R0C 5,100 TB
WDS400T2X0E 2,400 TB

Price history

US · cheapest per day

WDS400T1R0C $1,443 WDS400T2X0E $790
zoomed · drag to zoom
$1,565 $907 $250 Nov 2024 Mar 2025 Aug 2025 Jan 2026 Jun 2026 Nov 2026
WDS400T1R0C WDS400T2X0E
Capacity 4 TB 4 TB
Form factor M.2 M.2
Interface NVMe NVMe
NAND type TLC TLC
Endurance (TBW) 5,100 TB 2,400 TB
DWPD 0.7 -
DRAM cache Yes Yes
Power-loss protection No No
Sustained write - -
Cost / TBW $0.186 $0.329
Price / TB $237.20 $197.50
Buy
$1,443
View at Amazon →
$790
View at Amazon →

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

WDS400T1R0C

No Backblaze failure data for this model.

WDS400T2X0E

No Backblaze failure data for this model.