If you're running any kind of RAID, you definitely want drives intended for that purpose, as normal "eco friendly" desktop drives may behave or respond in such a way that they can cause the RAID to fail.

Otherwise, much of the differentiation (and pricing) of drives is simply due to expected workload, reliability, and warranty offered. A normal desktop drive designed for standard use with a standard 2-year warranty probably won't do well in a demanding 24x7 environment.

Just over a week ago I had a 4-drive RAID array fail. The drives were 4.5 years old. I replaced them with a new array with enterprise-grade drives with 5-year warranties. They cost more than the desktop or even "light duty" RAID drives, but hopefully they'll last.