Backblaze Hard Drive Failure Rates January 1 - March 31, 2015:
https://www.backblaze.com/blog/best-hard-drive/According to BackBlaze, Hitachi drives are the most reliable with an average annual failure rate of about 1%. Seagate's ST3000DM001 is at the bottom of the heap at 26%. However Seagate's ST4000DX000 model fares much better at 5% and the ST4000DM000 is at 3%.
Western Digital's Red 3TB/4TB/6TB (WD30EFRX/WD40EFRX/WD60EFRX) drives are failing at the rate of 13%, 9%, and 8% respectively.
On the basis of these results, it doesn't appear that enterprise drives are any more reliable than desktop models. In fact the converse appears to be the case. Moreover, BackBlaze have decided to purchase more ST4000DM000 consumer grade desktop drives for their datacentre.
If I were building a RAID, I would mix up my drives rather than sticking with only one model. ISTM that putting all your eggs in one basket defeats the purpose of redundancy. Moreover, if you have a power supply failure, WD's drives fail catastrophically, often requiring expensive data recovery, whereas other brands can usually be rescued with a $50 DIY PCB swap and firmware transfer.