Any drive is bound to fail eventually. WD Black are guaranteed for 5 years, Reds are I think three years, but Reds are for 24/7 operation. You can get the Seagates much cheaper with I believe up to a two year guarantee. I like the Seagate cause of the price difference, I paid 89 for my 2Tb, and I like it a lot, way more space than my old 1Tb drive. That being said, all three of my 1Tb drives failed, 1 Hitachi, 1 Seagate, and 1 F1 Spinpoint (which at the time were supposed to be about the best bang for the buck)
If your RAID is redundant so if a drive fails you can replace it, Seagate is a good choice cause of the price, if you can afford paying double for it, the WD Blacks can't be beat, Reds, somewhere in the middle.