Both of these drives show up in the same search results when someone types “cheap SSD upgrade” into Google, which is a little misleading because they’re not really competing for the same job. The Kingston A400 is a budget SATA SSD. The WD Green 240GB is also a budget SATA SSD, but WD has used the Green name on both actual SSDs and old-school 5400RPM hard drives over the years, so it’s worth being precise: this comparison is SSD to SSD, both at 240-250GB capacity points.
If you’re trying to decide between these two for a laptop upgrade or a secondary drive in a desktop, the honest answer is that the difference between them is smaller than the difference between either of them and an actual hard drive. But there are a few real distinctions worth knowing before you buy.
What you’re actually buying
The Kingston A400 has been around since roughly 2017 and is one of the best-selling SSDs on Amazon purely on price. It uses a SATA III interface, capped at 6Gb/s, and depending on when and where you buy it, Kingston has shipped it with different NAND and controller combinations without changing the model name. Early units used TLC NAND with reasonable performance; later production runs quietly switched to QLC NAND on some capacities, which drops sustained write speeds once the cache fills up. Kingston doesn’t advertise which version you’re getting, and it’s changed more than once, which is the biggest knock against the line.
The WD Green SSD line is WD’s entry-level SATA drive, sitting below the WD Blue in their lineup. It also uses QLC or TLC NAND depending on capacity and revision, and like the A400, performance is adequate for boot drives and light use rather than anything demanding.
Neither drive is aimed at power users. Both are aimed at people replacing a dying hard drive or adding storage to an older machine without spending much money.
Specs side by side
| Spec | Kingston A400 (240GB) | WD Green SSD (240GB) |
|---|---|---|
| Interface | SATA III (6Gb/s) | SATA III (6Gb/s) |
| NAND type | TLC or QLC (varies by batch) | QLC or TLC (varies by capacity/revision) |
| Sequential read (rated) | Up to 500MB/s | Up to 545MB/s |
| Sequential write (rated) | Up to 350MB/s | Up to 465MB/s (drops after cache fills) |
| DRAM cache | No (DRAM-less) | No (DRAM-less) |
| Endurance (TBW) | ~80TBW | ~60-80TBW depending on revision |
| Warranty | 3 years | 3 years |
| Typical street price (240-250GB) | Usually the cheaper of the two | Usually a few dollars more |
Those rated speeds are marketing numbers measured on empty drives with large sequential transfers. In day-to-day use, both drives feel similar: noticeably faster than a hard drive at boot and app launch, but not fast in the way a NVMe drive is fast. Random 4K performance, which matters more for OS responsiveness than sequential numbers, is unremarkable on both.
Where cheap SSDs show their limits
Both drives are DRAM-less, meaning they don’t have a dedicated memory chip to hold the mapping table for where data lives on the NAND. Instead they use a small portion of the host system’s RAM or rely on the NAND itself (HMB, or no buffer at all depending on controller). This isn’t a dealbreaker for a boot drive or a drive that mostly stores files you read rather than rewrite constantly, but it does mean sustained write performance tanks once you’re copying more data than the small DRAM-less cache can absorb. Copying a 100GB video folder onto either of these will start fast and then crawl.
QLC NAND, when present, also has lower write endurance than TLC and tends to slow down more as it fills up, because QLC needs more complex error correction and the controller has less margin to work with. For a drive that’s mostly idle, holding Windows and a browser, this never becomes visible. For a drive handling constant video editing scratch files or database writes, it will.
Neither drive is a good fit for heavy sustained workloads. If that’s your use case, step up to a drive with DRAM and TLC NAND, which usually means spending $5-15 more at this capacity, or look at NVMe SSDs if your motherboard has an M.2 slot, since those start outperforming any SATA drive regardless of NAND type.
Which one to actually buy
At 240GB, price is usually the deciding factor, and it moves around enough that whichever is cheaper on a given day is the one to buy. Neither is meaningfully better in a way you’d notice in daily use. If I had to pick a tiebreaker, WD’s rated write speed is a bit higher on paper, but the real-world gap closes once the cache fills on either drive, so I wouldn’t pay extra for it.
The bigger decision isn’t A400 vs Green, it’s whether 240GB is even enough. That capacity fills up fast once you account for a modern Windows install (15-20GB), updates, and a handful of games or applications. If this is a boot drive only, with a separate larger hard drive or SSD for files, 240GB is fine. If it’s the only drive in the machine, I’d budget for 480GB or 1TB instead, since the per-gigabyte price drops significantly at those sizes anyway. It’s worth browsing 1TB SATA SSDs before committing to a smaller drive just because it’s a few dollars less upfront.
Either of these drives is a legitimate upgrade from a mechanical hard drive, and both will outlast their 3-year warranty in a typical home PC. Just don’t expect either one to be a fast drive by current standards. If you’re replacing a hard drive, the jump feels big. If you’re comparing SSDs to other SSDs, the jump from either of these to a mid-range TLC drive with DRAM is the one that actually matters, and it’s a smaller price gap than people expect. For most casual builds, though, a basic budget SATA SSD like either of these does the job without drama.
