I voted for SMB, but the poll options you've chosen kind of confuse me. There are two on there that simply aren't file-sharing protocols at all (transfer, yes; sharing, no), and a third (WebDAV) that, honestly, seems like kind of an odd one to mention. And then you don't mention NFS at all. Maybe it'd be helpful for you to explain your use case in a little more detail--if, e.g., SFTP is on the table, maybe it isn't file storage in the normal sense.
For "normal" network file-sharing, SMB would be the protocol of choice for Windows or Mac clients; *nix clients could use either that or NFS.