Random IO

Random read/write performance matters if you copy a lot of small files or use the drive as storage for games/applications that are directly started off the drive.

Sequential IO

Sequential performance is relevant when you copy large files—videos, for example.

Sustained Write Speeds

Sequential write speeds start out at 300 MB/s until 32 GB have been written. Beyond that, speeds drop to 80 MB/s, which is slower than a mechanical HDD. Just like with all drives supporting pseudo-SLC, rates recover fairly quickly when writes stop and the SLC cache gets flushed to TLC. Still, it means you shouldn't copy huge chunks of data in one go.