UFS or ZFS

hi all,

made a freeNAS server its up and running but i want to know what format to use for my HD's UFS or ZFS

i have heard UFS is rock solid and ZFS is fast also includes added features snapshot, replication

i have 5x1TB drives so i can use RAID 5, im using it to backup importnat data, im using it for all the time machine to back up all the macs

any views thoughts what i should do?

rob