Short answer: for most people, an internal SSD with a DRAM cache or host memory buffer and TLC NAND on a PCIe 4.0 slot is the sweet spot. Headline read speed is the number every box leads with, and it is the one you will notice least once Windows has booted.
Below is each spec in the order it usually appears on a listing, what it means, when it matters, and when you can skip past it. Every section ends with a link to our SSD finder so you can see real drives side by side.
Interface: SATA, PCIe 3.0, 4.0 and 5.0
The interface sets the ceiling. SATA drives such as the Crucial MX500 and Samsung 870 EVO are rated around 560 MB/s. PCIe 3.0 x4 drives top out near 3,500 MB/s, PCIe 4.0 near 7,450 MB/s, and PCIe 5.0 drives like the Samsung 9100 PRO are rated close to 15,000 MB/s.
When it matters: only if your motherboard slot supports it. A PCIe 5.0 drive in a PCIe 4.0 slot runs at PCIe 4.0 speed.
When it doesn't: game loads and app launches barely change between a good PCIe 4.0 drive and a PCIe 5.0 one. The jump from SATA to any NVMe drive is the one you feel.
Sequential read and write
These are the big MB/s numbers on the box. They describe long, continuous transfers such as copying a large video file.
When it matters: moving big files often, video editing, or filling a drive with a game library in one go.
When it doesn't: everyday use is made of small, scattered reads, where the difference between 5,000 and 7,000 MB/s is hard to notice. Compare the WD Black SN770 with the WD Black SN850X and you will see the gap on paper is bigger than the gap on a desktop.
DRAM cache, HMB or neither
A DRAM cache is a small memory chip that holds the drive's map of where data lives. Drives without one either borrow a little of your system RAM (called HMB, host memory buffer) or go without.
When it matters: heavy multitasking, long sustained writes and older systems. A drive with DRAM, like the Samsung 990 PRO, keeps its pace more consistently.
When it doesn't: a modern NVMe drive with HMB, such as the Samsung 990 EVO Plus or Lexar NM790, is fine for gaming and general use. SATA drives cannot use HMB, so a DRAM-less SATA drive is the one to avoid if you have a choice.
TLC vs QLC NAND
TLC stores three bits per cell, QLC stores four. QLC is cheaper per terabyte and slows down more once its fast write cache fills up.
When it matters: large, sustained writes and drives you plan to keep nearly full.
When it doesn't: a QLC drive like the Crucial P3 Plus makes sense as a big game library drive, where you mostly read and rarely write. For your main drive, TLC is the safer pick.
Write cache (SLC cache)
Most drives write to a fast cache first and move the data to the main NAND later. Once that cache fills during a very large transfer, write speed drops. Makers rarely list the cache size, which is why two drives with the same headline speed can behave differently on a big copy.
When it matters: copying hundreds of gigabytes at once.
When it doesn't: normal daily use rarely writes enough in one go to fill it.
Endurance (TBW)
TBW is the total terabytes the maker guarantees you can write before the warranty runs out. Higher is better, and it usually scales with capacity.
When it matters: video work, scratch disks and servers.
When it doesn't: typical home use writes a small fraction of a drive's rating over its life.
Form factor
M.2 2280 is the standard desktop and laptop size. 2230 drives such as the WD SN770M and Corsair MP600 Mini fit handhelds like the Steam Deck. 2.5-inch drives are SATA.
When it matters: always check the slot length in your device manual before you buy.
Portable SSDs: the cable sets the speed
A portable drive can only go as fast as its connection. 10Gbps USB drives like the Samsung T7 Shield are rated around 1,050 MB/s. 20Gbps drives like the Samsung T9 are rated around 2,000 MB/s, but only on a port that supports 20Gbps. Thunderbolt 5 drives like the LaCie Rugged SSD Pro5 go further, again only on a matching port.
When it matters: check your laptop's port before paying for a faster drive.
How to use this
Start with your slot and budget, then pick TLC with DRAM or HMB, then look at speed last. Our SSD finder sorts internal and portable drives by Speed Score, and every product page lists the interface, cache and NAND type so you can check the specs that matter to you.
Which spec do you check first when you buy a drive? Tell us at hello@consumercarts.com.