The Apple iMac Late 2013 has a Flash storage medium which is faster than most similar spec computers that have been on the market for more than two years. Most computers that are a similar age to it have a Fusion Drive storage medium. Flash Drives 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.
A Flash storage medium is in fact the best storage speed across all similar spec PCs that came out more than two years ago.
Across similar types of computer the worst storage speed is HDD.