well, P1 is using QLC just like intel 660p, but it also have DRAM. in my experience, the problem of adata xpg sx6000 pro is when they decide to switch from silicon motion controller to realtek. realtek have less experience and thats why the consistency is quite rough. i already bought dozen of xpg ssd to upgrade my customers notebook, most of earlier version of sx6000 pro still used silicon motion controller, and performance was better (or at least more consistent), then came the sx6000 lite with realtek controller. months later all pro model were also switched to realtek one. The price go lower, but the write performance take a toll. In windows notebook, it still perform well, since the HMB seems to work just fine, but on macbook pro, the write performamce is stuck around 500Mb/s (on par with SATA SSD).I had both a Crucial P1 and this drive (Crucial came in my laptop, bought the SX6000 pro), and having swapped them between the laptops they were in to compare (Dell Latitude 7490 and Dell Latitude 5289), I was far more impressed with the performance of the SX6000 pro than I ever was with the P1. While I haven't had a 660, given the P1 is identical other than firmware, and the sx6000 pro is usually the same price or a few dollars less every time I look for a new drive, I'd take this any day over a 660.