An M.2 SSD is just a type of SSDs that is in a smaller shape. The data transfer speed of an SSD more relies on the interface. For an NVMe-based or PCle-based M.2 SSD, it is faster in data transfer rate than that of a SATA SSD. But the SATA M.2 SSD has a similar or the same data transfer speed when compared with a SATA SSD.