We use AS SSD version 1.6.4237.30508 test to benchmark the speed of copying files within a single partition the size of the whole SSD. The SSDs are tested in their steady state.
Reading and writing in parallel proves to be more difficult for the newer Plextor products. The company doesn't seem to optimize its firmware for such loads. The result is that the M3 Pro and M3S series are ahead of the newer Plextor drives, yet the Plextor M5 Pro and M5S aren’t hopeless, either. They are just average in this test.