You may think Hard Drives are all the same, and that there is no reason to upgrade unless you need more space, however that is NOT the case. Drives are getting faster and faster all the time, with more and more cache.
Take for example this mac mini with the standard 5400 RPM Hitachi Laptop Drive, it was replaced with a 7200 RPM Western Digital Black Drive. The drive benchmarks over 3 times higher, and the system has a dramatic performance boost.
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