The Drobo's virtual volume can be as large as 2TB allowing capacity to be easily expanded.
The Dashboard keeps you up to date with used and free space on the appliance.
The format tool offers plenty of choices and allows you to decide on the volume size.
You can mix drive capacities and there are plenty of warnings if one fails.
Considering its price, the DroboShare unit doesn't add a lot of value as a NAS facilitator.