Compare WD_BLACK SN850X 4TB and Lexar NM790 4TB: prices, speeds, $/TB. Which to buy in May 2026? Full spec breakdown.
Both the WD_BLACK SN850X 4TB and Lexar NM790 4TB sit in the Gen 4 category at 4 TB, so the matchup turns on controller efficiency, cache topology, and current pricing rather than raw class differences.
Hardware-wise, the WD_BLACK SN850X 4TB runs on WD's second-generation G2 in-house controller, tuned for sustained gaming I/O. The Lexar NM790 4TB pairs MaxioTech's MAP1602 silicon, the default choice for budget Gen 4 drives in 2024-2026.
Price separates these two meaningfully. The Lexar NM790 4TB costs $67.25/TB versus $89.75/TB for the WD_BLACK SN850X 4TB — a 25% premium that needs justification in real benchmarks, not just spec-sheet bragging.
The WD_BLACK SN850X 4TB carries a dedicated DRAM chip for FTL (Flash Translation Layer) mapping; the Lexar NM790 4TB relies on HMB (Host Memory Buffer), borrowing 64 MB from system RAM. The practical gap shows up only under sustained random write loads.
For PS5 expansion, both are PCIe Gen 4 M.2 2280 drives that meet Sony's minimum spec (7,300 MB/s read). The console can't take advantage of speeds beyond that, so save money by choosing the Lexar NM790 4TB. Both drives use the 2280 form factor, which is too long for Steam Deck or ROG Ally — you'd need a 2230 variant if either manufacturer offers one, or a dedicated handheld-format drive instead.
Pick the WD_BLACK SN850X 4TB if you value a dedicated DRAM cache chip. 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.
Pick the Lexar NM790 4TB if you value the lower retail price ($269 vs $359), and better $/TB economics ($67.25/TB). Budget-tier drives like the Lexar NM790 4TB have closed the gap with premium NVMes — the MAP1602 controller is genuinely competitive for everyday workloads at half the price.