If there is a NUC available with Thunderbolt, I would suggest looking at the Promise Pegasus. We have the 4-bay version in the office hooked up to a Mac Mini. We virtualize a Windows Server 2003 AD controller/file server and Terminal Services box (2 VMs total) on this machine. The VMs and their storage are hosted on the Promise box. The internal storage of the Mac Mini really does nothing but contain OS X. With the Mini's internal storage being composed of laptop drives in a RAID 0 array, I would assume the Promise has faster throughput. But I really have no evidence to back up that statement. All I know is that the Quad i7 Mac Mini running Parallels Server VMs over Thunderbolt is faster, quieter, and more reliable than the physical machines it replaced.

The great thing about the Drobo is the ability to mix and match drives. The Drobo S I have at home started with (5) 1.5TB drives. Then over time it switched to all 3TB drives, and now three of those are 4TB drives. Increasing storage space without having to rebuild the array is really convenient and it actually works these days. If I need more storage at work, I would have to offload the data from the Promise, rebuild the array, then load it back on just like any other RAID 5 setup.