What you’re actually choosing between
512GB is the sweet spot where this comparison gets interesting. It’s enough for an OS, a chunk of games, and daily files, but small enough that the price gap between SSD and HDD still matters to a lot of budgets. At smaller capacities SSDs win outright because cheap HDDs under 500GB barely exist anymore. At larger capacities HDDs win on cost per gigabyte by a wide enough margin that bulk storage still makes sense. 512GB sits right in the middle, so the decision actually depends on what you’re using the drive for.
Speed: not a small gap
A 512GB SATA SSD reads and writes around 500-560 MB/s sequentially. A 512GB NVMe SSD on a decent PCIe 3.0 or 4.0 interface hits anywhere from 2,000 MB/s to 7,000 MB/s depending on the controller and interface generation. A 512GB-class 2.5″ HDD (these are increasingly rare; most HDDs now start at 1TB) runs 80-160 MB/s sequential, and that number craters to single digits when the drive is doing random reads, like loading an OS or opening a folder with thousands of small files.
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That random-access weakness is the real story. Sequential speed sounds good on a spec sheet, but what makes a PC feel slow is small random I/O: boot files, registry lookups, game asset streaming, thumbnail generation. HDDs are mechanically limited here because a physical head has to seek across spinning platters for every scattered read. SSDs have no such penalty. This is why swapping a boot drive from HDD to SSD is the single biggest “feel” upgrade you can make to an old PC, often more noticeable than a CPU or RAM upgrade.
Price per GB at 512GB
Rough current market numbers, these move constantly but the ratios hold:
| Drive type | Typical price (512GB-ish) | Cost per GB | Sequential speed |
|---|---|---|---|
| SATA SSD | $30-45 | ~$0/GB | 500-560 MB/s |
| NVMe SSD (Gen3/Gen4) | $35-55 | ~$0-0.10/GB | 2,000-7,000 MB/s |
| 2.5″ HDD (where available) | $35-50 for 500GB class | ~$0-0.10/GB | 80-140 MB/s |
| 3.5″ HDD (1TB, for reference) | $40-50 | ~$0-0.05/GB | 150-220 MB/s |
Notice that at 512GB specifically, SSDs and HDDs are often priced within a few dollars of each other. That price-per-GB advantage HDDs are known for only shows up clearly at 2TB and above. At this capacity, there’s no real financial reason to buy a hard drive unless you specifically need the archival traits HDDs have.
How they actually fail
HDDs fail mechanically: bearing wear, head crashes, stiction on startup after sitting unused, or physical shock damage if dropped while spinning. Annualized failure rates in backblaze-style field data usually land between 1-2% per year for drives in active service, climbing after year 3-4. When an HDD fails, it’s sometimes partial, you’ll get bad sectors and slow degradation before total failure, which gives you warning.
SSDs fail electrically: controller failure or NAND wearing out after a given number of write cycles (rated in TBW, terabytes written). A typical 512GB consumer SSD is rated for 150-300 TBW, which for a normal user is 10+ years of writes. SSD failure is often sudden and total, the drive just disappears, with less warning than a dying HDD. SSDs are also immune to physical shock, which matters for laptops.
Neither of these failure modes is a backup strategy. Both drive types fail. If the data matters, it needs to exist in two places regardless of which drive you buy.
When the HDD is still the right call
At 512GB specifically, I’d only recommend a hard drive in a few cases: you’re adding a second drive purely for passive file storage like media libraries or backups where speed doesn’t matter, you’re working with an older system that only has a SATA port and no M.2 slot and the budget is extremely tight, or you need the drive for something write-heavy and continuous like a surveillance DVR, where SSD endurance math gets worse than HDD mechanical wear over years of constant writing.
Outside of those cases, buy the SSD. For a boot drive or primary drive in anything you interact with daily, the usability difference is not subtle. If you’re shopping, a 512GB SATA SSD is the safe universal choice for older laptops and desktops, while a 512GB NVMe SSD is the better pick if your motherboard has an M.2 slot, since you get several times the speed for a few dollars more.
What I’d actually buy
If this is a boot drive or your only drive: SSD, no debate. The HDD’s only advantage, raw cost per GB, basically disappears at 512GB. If you need bulk storage alongside your SSD, like a media server or large game library, that’s where a 2TB internal hard drive starts making financial sense instead, since the per-GB savings actually show up at that size.
The real mistake isn’t picking HDD over SSD, since few people do that intentionally anymore. It’s buying a 512GB HDD today for a boot drive, out of habit or because it was in a prebuilt, when a same-priced SSD was sitting right next to it on the shelf.
