Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | Samsung - T9 Portable 2TB | WD - Black SN850X 2TB |
|---|---|---|
| Sequential read | 2000 MB/s | 7300 MB/s |
| Sequential write | 1950 MB/s | 6600 MB/s |
| Interface | USB 3.2 Gen 2x2 | PCIe 4.0 x4 |
Between the T9 Portable 2TB and Black SN850X 2TB, the T9 Portable 2TB comes out ahead in interface, while the Black SN850X 2TB wins on sequential read / sequential write. Overall, the T9 Portable 2TB scores 64.1 and the Black SN850X 2TB scores 68.7 on our Mars Score.
Which should you buy?
The Black SN850X 2TB edges ahead on the Mars Score (64.1 vs 68.7), but the 4.6-point gap is small enough that the right pick comes down to which spec advantages matter to you.
Pick the T9 Portable 2TB if you care most about interface. The biggest gaps in its favor are interface. The single most decisive one: Interface: USB 3.2 Gen 2x2 (vs PCIe 4.0 x4).
Pick the Black SN850X 2TB if you care most about sequential read / sequential write. Its strongest claims are sequential read, sequential write. The single most decisive one: Sequential read — 265.00% more. 7300 MB/s vs 2000 MB/s.
Both ship with comparable capacity, endurance (tbw), so those specs do not separate the two — focus on the differences below.
Bottom line: there is no wrong answer here — match the spec advantages to how you actually use the product. The Mars Score parity says both are well-rounded; the differences are about trade-offs, not quality.
Which should you buy: Samsung - T9 Portable 2TB or WD - Black SN850X 2TB?
WD - Black SN850X 2TB leads the current Mars Score by 4.6 points.The more useful decision is the trade-off behind that result: compare sequential read, sequential write, interface against the way you will actually use the product.
Choose Samsung - T9 Portable 2TB if…
Samsung - T9 Portable 2TB has the measurable edge on interface.
Choose WD - Black SN850X 2TB if…
WD - Black SN850X 2TB has the measurable edge on read mbps, write mbps.
This is a structured comparison of the published catalog values. It is not a claim of identical real-world performance across every workload; use the linked spec drill-downs and methodology page to inspect the inputs.
Why Samsung - T9 Portable 2TB wins
- ▲Interface: USB 3.2 Gen 2x2 (vs PCIe 4.0 x4).
Why WD - Black SN850X 2TB wins
- ▲Sequential read — 265.00% more. 7300 MB/s vs 2000 MB/s.
- ▲Sequential write — 238.46% more. 6600 MB/s vs 1950 MB/s.
Spec comparison
Capacity
| Spec | Samsung - T9 Portable 2TB | WD - Black SN850X 2TB |
|---|---|---|
| Capacity | 2000 GB | 2000 GB |
Performance
| Spec | Samsung - T9 Portable 2TB | WD - Black SN850X 2TB |
|---|---|---|
| Sequential read | 2000 MB/s | 7300 MB/slead |
| Sequential write | 1950 MB/s | 6600 MB/slead |
| Interface | USB 3.2 Gen 2x2lead | PCIe 4.0 x4 |
| Form factor | Portable USBlead | M.2 2280 |
Endurance
| Spec | Samsung - T9 Portable 2TB | WD - Black SN850X 2TB |
|---|---|---|
| Endurance (TBW)ⓘ | 1200 | 1200 |
| Warranty | 5 yrs | 5 yrs |