Compare WD_BLACK SN8100 4TB and WD_BLACK SN850X 4TB: prices, speeds, $/TB. Which to buy in July 2026? Full spec breakdown.
WD_BLACK SN8100 4TB vs WD_BLACK SN850X 4TB pits two different generations against each other at 4 TB. The question isn't which is faster on paper — that's settled — it's whether the bandwidth gap shows up in your specific workload.
Hardware-wise, the WD_BLACK SN8100 4TB runs on SMI's SM2508 silicon, which became the default Gen 5 controller for power-conscious flagships. The WD_BLACK SN850X 4TB pairs WD's second-generation G2 in-house controller, tuned for sustained gaming I/O.
There's a modest pricing advantage for the WD_BLACK SN850X 4TB: $133.75/TB compared with $175.00/TB. For typical gaming and productivity, this becomes the deciding factor when specs are close.
On sequential reads the WD_BLACK SN8100 4TB pulls ahead by 7,600 MB/s (14,900 MB/s versus 7,300 MB/s). That matters for moving large files but rarely shows up in game loads.
Write speeds skew toward the WD_BLACK SN8100 4TB: 11,000 MB/s sustained against 6,600 MB/s. Content creators feel this; gamers do not.
If this purchase is for a PS5 storage expansion, the comparison flattens — Sony's PCIe Gen 4 controller normalizes both WD_BLACK SN8100 4TB and WD_BLACK SN850X 4TB to roughly equal in-game load times. The cheaper drive is the smart pick. The leap from Gen 4 to Gen 5 doubles peak throughput on paper but produces single-digit-percent improvements in game load times, OS boot, and most productivity benchmarks. The WD_BLACK SN850X 4TB is the better default unless you have a specific workload that needs the extra lanes. Video editors will gravitate toward the WD_BLACK SN8100 4TB for its write headroom (11,000 MB/s sustained). Project saves and proxies move faster, which compounds across a workday. Heads-up — these are full-length 2280 drives. Steam Deck and most current handhelds require shorter 2230 modules, so check capacity-specific 2230 variants if that's your target platform.
Market context: the WD_BLACK SN8100 4TB ranks #3 of 6 Gen 5 4 TB drives we track by $/TB, while the WD_BLACK SN850X 4TB ranks #4 of 6 Gen 4 4 TB drives. Neither is a value leader right now — if $/TB is your priority, check the cheaper alternatives below before committing.
As of July 27, 2026, these tracked drives undercut both the WD_BLACK SN8100 4TB and WD_BLACK SN850X 4TB on $/TB:
Pick the WD_BLACK SN8100 4TB if you value meaningfully faster reads (14,900 MB/s), and higher sustained writes (11,000 MB/s).
Pick the WD_BLACK SN850X 4TB if you value the lower retail price ($535 vs $700), and better $/TB economics ($133.75/TB). The SN850X has been the best-selling Gen 4 NVMe in PCPartPicker builds for two consecutive years — Game Mode 2.0 prioritizes I/O when supported titles need it.