The Lenovo Flex has an HDD storage medium which is better than the SSD storage medium found on most 2 in 1 laptops that have been on the market for around the same time as it. HDD is a traditional storage drive which stores the information on magnetic disks. HDD drives are slower than other forms of storage such as solid state drives (SSD) and flash drives.
An HDD storage medium is actually the worst storage medium amongst all 2 in 1 laptops that have been around for a similar time to the Flex.
Amongst similar types of portable PC the best storage medium is SSD.