The complexity fear is understandable as I went through the same rational when setting up samba shares at remote sites. For these I had no choice but to use samba though as there was no local Windows servers.
Both of your alternatives have pro's and con's. I'll let you decide weather each point is a pro or con for your circumstances.
ZFS + CIFS:
- Setup and testing will be more involved.
- Files will be accessible from the Solaris server.
- Once setup, extra permissions and shares can be setup from a Windows machine. (Ie, you only need to go through setup once.)
- Speed benefit from direct file access via the Solaris machine.
- Access to CIFS can not be via FQDN, only by hostname (as of oi148)
iSCSI, Shared via Windows mount
- Increased network traffic.
- No more file access from the Solaris server.
- Easier initial setup.
- Extra shares and permissions are still administered the same way.
Either way you go the most important part is good documentation to ensure the setup is easily reproducible, and backups to your satisfaction. My preference would be to use ZFS + CIFS for speed and native file access. The overhead of the extra permissions and LDAP lookups has been a non issue for me as the lookups are cached for some time and increase traffic far less than the iSCSI overhead.