The Mac Mini Late 2014 has an SSD storage medium which is faster than most personal computers that were launched more than two years ago. Most comparable spec personal computers that are a similar age to it 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.
This desktop computer's storage speed (SSD) is in fact the best storage speed amongst all PCs of this age and spec.
The worst storage speed across comparable types of desktop computer is HDD.