I'll be getting a larger SSD, probably a Crucial MX500.
Should I get a SATA drive or M.2? If I understand correctly, M.2 is better in benchmarks, but the difference isn't that big in actual use.
A couple things. SATA and m.2 aren't really
how you compare them.
SATA is a protocol, and when people say "SATA SSD" these days I'm assuming they're generally talking about 2.5" SSDs. The 2.5" part of it is the form factor. Almost universally, any 2.5" SATA SSD these days is going to push the limits of the SATA connection. Somewhere in the 500-560 MB/s transfer rate for both sequential reads and writes.
m.2 is a form factor. Generally (again, this is similar to SATA in that people use a colloquial term but may not necessarily know what it means), m.2 drives can be based on the NVMe protocol. It's newer and faster than SATA, and definitely has some advantages that SATA just can't match in its current state. Thing is, you can have SATA drives in the m.2 form factor, which means they won't be any faster than the 2.5" SATA version of the drive.
Choosing between the two protocols (SATA and NVMe) is the real decision. Do you need blistering speeds upwards of 1500 MB/s plus that NVMe offers? No? OK stick with 2.5" SATA if your motherboard and case permit it. There aren't a ton of m.2 SATA drives to choose from in the first place so if your budget permits it just get NVMe (like a Samsung 970 EVO or ADATA or whatever).
For 99.3 percent of people SATA (2.5" or otherwise) is going to be plenty for the time being. I'd suggest you stick with that, but your workload might be begging for NVMe. What are you planning on using the SSD for?