Samsung's 3-D V-NAND was a revolutionary development. Traditional 2-D NAND started to become unreliable below 20nm, and the addition of TLC, not to mention QLC, only made that much worse. Samsung's 3-D V-NAND increased the architecture size to a roomier 30nm to 40nm while expanding into 3-D. Samsung used this 3-D V-NAND starting with the 850 Pro and 850 EVO consumer drives and SM863 and PM863 enterprise drives, with all of these drives being fast enough to saturate SATA III.
The 850 Pro is a very nice SSD and works very well for laptops, but the SM863 and PM863 added power loss protection in the form of tantalum capacitors which allowed data still in transit to finish the journey. This means that SSDs used as desktop system drives without a UPS won't brick if the power suddenly disappears.
The SM863 bests the PM863 because the former is MLC while the latter is TLC, with every "LC" generation having a tenfold reduction in reliability and endurance. The 850 EVO is also TLC.
And both the SM863 and PM863 use the enterprise version of Samsung's Magician, which is a CLI versus the telemetry-gathering Magician for consumer SSDs. Only those who have secure-erased SSDs can appreciate the difference. With Samsung's consumer Magician, Intel SSD Toolbox, hdparm in Linux, and other consumer utilities, the SSD has to be removed after the process starts to unfreeze -- in the logical sense, not the temperature one -- while DC Magician just works.
SSDs are becoming faster, though in PCIe form factors, but the SM863 will be remembered as one of the best 2.5" SSDs ever made, along with Intel's DC S3700 with specially chosen HET NAND and Intel's 730 with factory overclocking and NAND almost as good as the DC S3700, with both Intel products also having power loss protection.