The Crucial MX500 M.2 1 TB doesn't hold any surprises as long as you are aware that it uses the SATA interface via PCIe and not NVMe. This means that peak transfer speeds are limited to about 500 MB/s due to the interface. So you're not going to see the flashy gigabyte numbers competing high-end NVMe drives provide. Rather, the MX500 M.2 gives you the MX500 2.5" in a more convenient form factor. Be aware, though, that adding a SATA M.2 drive will not magically give you more SATA connectivity. All motherboards support a fixed number of SATA drives and that capability is shared between the cabled ports and the M.2 slots (when they use SATA). Your motherboard manual will tell you which SATA port gets disabled when a SATA SSD is installed in its associated M.2 port.

Average performance numbers of the MX500 are excellent and are closely competing with the best SATA drives in our test group. NVMe SSDs are about 10%–15% faster, depending on the application, of course. Against an NVMe drive, the MX500 will lose big time when it comes to large-file copying, but it can keep up very well in the other tests. The underlying reason is that even SATA SSDs are mostly fast enough for today's consumer applications as the bottleneck has shifted to CPU/memory/Windows API and program code.

Compared to the MX500 2.5" SATA version, our synthetic latency testing shows improvements which translate into small performance differences. Crucial commented that this is most likely due to the updated firmware (M3CR020 vs. M3CR010), which should become available for the 2.5" SATA drives soon.

Unlike many other TLC drives, the "write-hole", which is caused by the SLC write cache getting full, is really small on the MX500. Where other drives drop to 200 MB/s writes or below, the MX500 will happily cruise along at over 400 MB/s, a drop that's barely noticed and that happens only after 32 GB have been written. Once the writes stop for a short moment, and the SLC cache has time to clear, write performance will return to full speed again.

While the MX500 M.2 comes with a thin metal heatspreader, it is no replacement for a real heatsink. The drive will thermal-throttle to around 300 MB/s when pummeled by non-stop writes for over 90 seconds. Before you panic: this is a rare scenario. You'd have to write around 45 GB without pause for the drive to get sufficiently warm—something that rarely happens. Still, if you often send such large bursts, then the SATA version might be a better choice because it can dissipate heat more efficiently due to its larger form factor. Reads are not affected by this and will always run at maximum speed.

Just like the MX500 2.5", the M.2's strongest suit is its pricing. With just $250, it is pretty much the most affordable SSD on the market that still offers good performance, sufficient for everyone except the most demanding users. The MX500 M.2 is a great choice for a small form factor PC where you don't want to deal with bulky 2.5" drives or the cable mess in a larger case. It's nice to see that Crucial is not charging a small-form-factor tax for the M.2 version—both the MX500 2.5" and M.2 are priced the same. All we now need from Crucial is an affordable high-performance M.2 NVMe SSD.