USAFRet :
Again...m.2 is simply the form factor.
An m.2 port that only accepts a SATA III drive (yes, there are a lot of them) provides exactly the same performance as a typical 2.5" SATA III drive in a regular SATA III port on the motherboard.
An m.2 port that accepts either will still only provide SATA III performance with a SATA III drive.
With an NVMe drive in an m.2 port that accepts it, then things get faster.
"m.2" is not there to provide faster speed, just to be a different package and connection type.
There are several drives that are available in either 2.5" or m.2 packaging.
The same drive and performance and price, just in a different package.
It was created to provide faster speeds due to the limitations of SATA... like I said just compare any M.2 to a standard SSD drive. You can easily obtain much faster speed then you could with a SSD drive due to the port limitations. Now yes, you use SATA on an M.2 you will get those speeds. But M.2 is able of obtaining much higher speeds, which is why it was created.
This is why M.2 even exists.
This is all I'm saying. SATA bottleneck exists. Technology used with the M.2 is what was created to bypass that limitation. M.2 drives are typically faster then standard SSD counter part, which was created because the M.2 slot can support those speed on the PCI bus. Using SATA port on an M.2 you would clearly hit the SATA limits aka bottleneck.
"First, a quick note about SSDs – they’re fast. So fast in fact, their limiting factor is not their own hardware, but rather the SATA III connection that hard drives have traditionally used. Enter NVMe. Standing for “Non-Volatile Memory Express,” NVMe is an open standard developed to allow modern SSDs to operate at the read/write speeds their flash memory is capable of. Essentially, it allows flash memory to operate as an SSD directly through the PCIe interface rather than going
through SATA and being limited by the slower SATA speeds. Put another way, it’s a description of the bus the component uses to communicate with the PC, not a new type of flash memory. It is also unrelated to the form factor, which is why NVMe drives can come in both M.2 or PCIe card form factors.
With both form factors, the component is connecting electrically to the PC via PCIe rather than SATA."
http://www.velocitymicro.com/blog/nvme-vs-m-2-vs-sata-whats-the-difference/
SATA port, using SATA interface = possible bottleneck. That is simply all I'm stating.