Well… iSCSI or NAS shoudl be quite clear if you take into account that you can't mount an iSCSI volume on more than one computer at the same time, except if you run some special file system on it, called a cluster file system like StoreNext from ADIC, Xsan from Apple, or a similar product for Microsoft.

If you want the share to be accessible from different computers at the same time, you'll stay with NAS if you want fast and flexible storage to a dedicated computer, iSCSI is the choice (at least for me).

Cheers,
budy