There is no "this is better than that" in storage. Every type has its advantages. A standard 3.5" HDD is super cheap and is available in a big capacity. A PCIe SSD is super fast, it even is about 5x faster than SATA SSD, but it's super expensive (double the price of SATA SSD while offering same capacity). A SATA SSD is between the two worlds. It's faster than the standard 3.5" HDD, but is more expensive than it. It's slower than the PCIe SSD, but is cheaper than it. I personally will buy all 3 of them. I will use 16 or 32GB of PCIe SSD as a boot drive, so it will boot the fastest. I will use 480-512GB SATA SSD as a game and program drive, so it will perform faster. I will usebat least 2TB of HDD as a media drive, since media doesn't need speed to perform well. In terms of mSATA and M.2, they're only form factor, in which the latter is smaller than the former.