The Lenovo Flex has an HDD storage medium which is better than the SSD storage medium found on most 2 in 1 laptops that are a similar age to 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.
This portable PC's storage medium (HDD) is in fact the worst storage medium amongst all laptops that have been around for around the same time as the Flex.
The best storage medium across similar types of portable PC is SSD.
Laptops with a better storage medium that might be worth considering include the Lenovo Yoga (£1,060.16) (SSD), or the HP Pavilion x360 (£382.39) (SSD).