RE3's are Server class SATA Hard Drives. They will for sure work in any RAID setup and are supposed to have a longer MTBF. Mean Time Before Failure. Although, you'd be hard pressed to find out what the MTBF is for the BE drives since it isn't listed anywhere. But they both have 5 year warranties, so they are probably the same in that regard.
I wouldn't hesitate to use BE drives in RAID. However, I would rather use Samsung Spinpoint F3's since they are significantly faster in RAID 0 and 1 and don't cost any more than the WD BE's.