The Esprimo E420 has an SSD storage medium which is faster than most PCs of this type and age. Most PCs of this type and age have an HDD storage medium. Solid State Drives (SSD) store information in transistors on a circuit board rather than on optical or magnetic media. This has the advantage of being much faster than a traditional HDD drive.
An SSD storage medium is in fact the best storage speed across all computers of a similar spec and age to the Esprimo E420.
The worst storage speed across comparable types of desktop computer is HDD.