Different context (NAS vs SAN). CIFS and NFS export files and filesystems, and can be safely accessed in RW mode by multiple clients, shared. GEOM gate presents complete devices to remote computers, more like iSCSI. While iSCSI/FC devices can be mounted by multiple client machines, leaving clients to deal with locking and concurrency (cluster/parallel filesystems), ggate exports 1 to 1. Any device presented to network via GEOM gates can be mounted on a single machine only.
Its application is completely limited to FreeBSD networks because it only runs on FreeBSD, both client and server. If you have an iSCSI system with 1:1 device mappings GEOM gates should perform faster. Note that ggates don't provide any security or authentication, only IP based export check (like NFS).
