SSD-market anno 2017
What can you purchase when it comes to 'classic' sata SSDs? In the low-end segment we still find some SSDs with outdated SandForce, JMicron and Phison controllers, but products with such a basis usually do not offer the performance and features that you want. In the mid segment we mostly find SSDs with controllers manufactured by Silicon Motion and Marvell, as well as Samsung MGX-controllers in the Samsung SSDs. A high-end segment no longer exists here; for the best performance you need to take a look at a PCIe-SSD.
More and more SSDs use TLC flash memory, which stores three bits per memory cell. The time that this type of memory was only used in budget products is truly over. The disadvantages in regards with the reliability are solved by the change to 3D NAND, where the memory cells are bigger than with smaller 2D-memory, but still take up less space because of the stacking. Furthermore the slower write performance of this type of memory is compensated for by using smart caching-methods. A part of the flash memory is often operated as SLC-memory, which means that there is a buffer of several gigabytes that allows for much faster write speeds.
Because the performance of sata-SSDs is very close, even in synthetic benchmarks let alone what is noticeable when used in practice, manufacturers try to distinguish themselves in other ways. For example, more expensive SSDs often have a longer warranty and sometimes software is supplied for RAM-caching. Many new SSDs are also explicitly commended because they use 3D NAND, but this is mostly an advantage for their cost price.
Much better performance is possible with SSDs that utilize a PCIe-interface, often in combination with the NVMe-protocol that was especially developed for that interface. They are a lot faster in synthetic tests, but you do not notice this as much in all programs. With a lot of tasks the storage is simply not the bottleneck, which means they are not performed faster when using a faster SSD. (Semi-)professionals that perform specific tasks or, for example, work with much bigger files can still benefit from using these products.