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.
"SMB1 is an extremely chatty protocol, which is not such an issue on a local area network (LAN) with low latency. It becomes very slow on wide area networks (WAN) as the back and forth handshake of the protocol magnifies the inherent high latency of such a network. Later versions of the protocol reduced the high number of handshake exchanges."