ChipFlip
SATA and NVMe SSDs both get called "fast" compared to a spinning hard drive, and that's true, but they're not the same kind of fast. If you're piecing together a used build and trying to decide where storage money actually goes, the gap between these two interfaces is bigger than most buying guides let on.
SATA is capped by the connector, not the drive
A SATA SSD like the TEAMGROUP AX2 512GB, currently $69.99 used, is limited to roughly 550 MB/s no matter how good the drive inside it is. That's the SATA III interface's hard ceiling, not a flaw in this specific drive. It's still miles faster than a mechanical hard drive for boot times and everyday responsiveness.
NVMe removes the ceiling entirely
An NVMe drive plugs directly into the PCIe bus instead of routing through the SATA controller, and that's the whole difference. The Samsung 990 Pro 2TB, running $250 used, and the WD Black SN850X 2TB, at $400 used, both push sequential speeds several times higher than any SATA drive can reach.
Do you actually feel that speed day to day? For boot time and app launches, less than you'd expect once you're already past a mechanical drive. Where NVMe genuinely earns its price is large file transfers, video editing, and any workload that reads or writes big chunks of data continuously.
So which one should you buy
If your motherboard has an open M.2 slot and your budget allows it, NVMe is the better long-term pick, especially at higher capacities where the per-gigabyte gap narrows. If you're stretching a tight budget or your board is out of M.2 slots, SATA still gets the job done for general use without the premium.
Bottom line
Don't pay NVMe prices for a build that's only doing basic web browsing and office work, a SATA drive handles that fine. Do pay it if you're editing video, moving large files regularly, or building something you plan to keep for years without a storage upgrade.