SMB1 was slow - very slow. Novell IPX/SPX was far faster.
SMB2 changed the protocol to include multiple operations in a single packet, but did not introduce encryption (and Microsoft ignored other SMB encryption schemes). It is a LOT faster.
SMB3 finally adds encryption, but only runs in Windows 8 and above.
NFS is a bit messy on the question of encryption, but is a much more open and free set of tools.