The Lenovo Flex 15D has an HDD storage medium which is better than the SSD storage medium found on most similar spec laptops that have been available for more than two years. 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 in fact the worst storage medium amongst all 2 in 1 laptops that have been available for a comparable time to the Flex 15D.
The best storage medium across similar types of notebook PC is SSD.
Notebook PCs with a better storage medium that might be worth considering include the Lenovo Yoga (SSD), or the HP Pavilion x360 (SSD).