The Mac Mini Late 2014 has an SSD storage medium which is faster than most medium processor core desktop computers that are a comparable age to it. Most medium processor core desktop computers that were launched around the same time as 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.
An SSD storage medium is actually the best storage speed amongst all medium processor core desktop computers that have been on the market for more than two years.
Amongst similar types of PC the worst storage speed is HDD.