The DELL OptiPlex 9020M has an SSD storage medium which is faster than the HDD storage medium found on most desktop computers of this age and spec. 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.
This PC's storage speed (SSD) is in fact the best storage speed amongst all personal computers that were launched more than a year ago.
The worst storage speed across comparable types of PC is HDD.