Once we use mechanical drives they become bigger and better priced. Then slowly SSD started to gain traction due to speed but storage was an issue and one can argue price and size with ssd is still an issue.
Todays newer motherboards have an M2 slot, one can use for example a samsung 960 evo m2 as a start up ssd a 256gb one. The main advantage with a M2 ssd is that small files reads and writes and speed is improved vs a sata ssd. When using windows or some other OS you want the most speed access reading small files and a samsung 960 evo excels at just that. I am using one fast sata ssd from samung a 850 pro for just that reason.
When you choose an ssd you want to buy for the workload and the small files for windows then a fast M2 ssd is a great choice. I am considering adding an M2 ssd to my computer.
SSD started with 2D flat plan nand cells, when they started to shrink those they run into electron migration that cells leaked and needed adjustments. A 2D nand ssd should be avoided. The option with 3D nand was that they could use a larger nand size process and then have way less leakage than smaller 2D nand. When samsung started the 3D nand wave they used a 32nm for 3D nand when 2D nand was hitting 16nm. Using a bigger nand manufacturing for 3D had great advantages, faster, better endurance and more reliable.
Yes the samsung 960 evo use 3D nand so does my sata ssd 850 pro.
So if your in for a upgrade with the SSD then a M2 ssd is a great option if your motherboard has such a slot. If not maybe its time to upgrade your computer for a new era of speed and usage.