I have both a MyBook and a Drobo connected to my Mac. The Mybook is much much quieter, but the Drobo provides data redundancy.

Sean’s note: The truth is that hard drives fail — so if you’re not using a RAID product with redundancy you’re always going to be at risk of losing data. Your safest choice would be a multi-disk system with the capability to do RAID 5 networking — any disk in that array could fail and you could still rebuild your backup simply by swapping the dead drive with a replacement. These solutions tend to be more expensive, however. The Drobo doesn’t use RAID but it’s designed to move data as necessary to protect it…and the advantage is that it doesn’t require you to match capacities of your hard disks like RAID does.