Two portable SSDs, one big gap: the NVMe-vs-SATA decision your speed test will confirm

The portable-SSD market sells the enclosure and hides the drive, and the two together are the product. A "1050 MB/s" box is a SATA drive at its ceiling or an NVMe drive at half its floor depending on the cable and the port; the whole shopping skill is knowing which number in the chain is the cap, and knowing the number the box does not print at all.

The two drive classes, one sentence each

• SATA (2.5-inch or M.2 SATA): the interface tops out just under the 550-600 MB/s burst region, and real sustained writes - the number that matters for the footage shuttle - land in the 400s, sometimes 300s, when the cache runs out. In a good enclosure on a USB 3 port it is a reliable, cool, boring machine.
• NVMe (M.2 in a proper enclosure): the drive's own bus is many lanes wide; the enclosures' USB bridges cap it - and the cap is where the shopping gets honest. USB 3.2 Gen 1 (the old 3.0, the name the market still blurs) is about 500 MB/s - exactly the SATA ceiling, so a Gen-1 NVMe box buys you nothing but heat; Gen 2 at roughly a gigabyte per second is where the NVMe starts to actually pay; Gen 2x2 and the Thunderbolt/USB4 tiers are the real speed lanes.

The trap: the number the box does not print

Burst speed is the marketing and sustained write is the truth: every drive has a small fast region (the SLC cache) that empties around the first tens of gigabytes, and after it does, the NVMe that "did 1,000" in the demo is writing at whatever its bare flash manages, which on a cheap drive with small cache and no DRAM can be at the SATA's own level - while running hot enough to throttle below it. The two honest purchase questions, therefore: what is the sustained figure in the drive's own spec table (not the enclosure's), and does the enclosure's aluminium shell actually touch the drive's label through a pad - plastic shells and air gaps are the reason a "Gen 2" box thermally throttles at minute nine of the transfer you cannot abort.

The decision, as a rule

Documents, backups, the office shuttle: SATA drive in a metal enclosure, and the money is better spent on the second copy. Video, disk images, the working drive for the editor's laptop: NVMe in a good metal Gen-2 enclosure minimum, from the brand whose spec table prints the sustained number, and the cable that came with the box treated as part of the drive. And on every laptop you plug into: check the port - the sticker that looks like a plain USB socket but is a 5 Gb/s one is the reason the "new fast drive" is as slow as the old one, and no product on the shelf fixes a bottleneck in the wall of the machine you already own.