The reason that NAS/Enterprise drives are necessary in some situations has to do with how RAID controllers deal with errors when encountered, which is different than standard controllers.
Western Digital refers to the feature on their Red drives as TLER (Time Limited Error Recovery
) but pretty much all of the NAS/Enterprise drives have a similar feature. In short what it does exactly what the name implies... it limits the amount of time the drive will spend trying to recover a bad block. While there is no great consequence in a typical desktop environment (other than the drive is temporarily unresponsive) in a hardware RAID environment, the controller will recognize the drive as unresponsive, and flag it as offline, necessitating a rebuild from parity data. Once that happens, the increased reads prompted by the rebuild increase the likelihood of encountering another error, which will then send the RAID into "failed" status (if only using single parity)
If you eliminate the RAID controller from the equation, you eliminate the need for drives that support TLER (or the equivalent)
That said, most NAS/Enterprise drives also include technology to compensate for the increased vibration of a multi-drive system. If you think that vibration isn't a significant issue with storage arrays, I suggest you watch
(h/t to @EricN) The point being that the amount of vibration it takes to affect a hard drive is probably much less than you would imagine, and consequently, vibration is a more significant issue than many people would think.
Desktop drives are generally going to be less reliable than NAS/Enterprise drive in large arrays. As mentioned above by @Mfusick, the WD Green drives are generally a poor choice. If you have a look at this thread
you can see the carnage of a Hardware to FlexRaid migration and the pile of Seagate and Hitachi drives that didn't survive the transition.
Many people find the features of NAS/Enterprise drives to be a worthwhile investment (other don't of course)
If it were me, and I had the budget to get the NAS drives, I would. The incremental difference in price for me is good insurance against having to start a "Anyone ever wish they did their Storage Server right the first time? (or better?)" thread. However if the budget is tight, it is certainly a reasonable place to save some money.