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."
I wonder if it would maintain a speed advantage today.
"NetWare dominated the network operating system (NOS) market from the mid-1980s through the mid- to late-1990s due to its extremely high performance relative to other NOS technologies. Most benchmarks during this period demonstrated a 5:1 to 10:1 performance advantage over products from Microsoft, Banyan, and others. One noteworthy benchmark pitted NetWare 3.x running NFS services over TCP/IP (not NetWare's native IPX protocol) against a dedicated Auspex NFS server and an SCO Unix server running NFS service. NetWare NFS outperformed both 'native' NFS systems and claimed a 2:1 performance advantage over SCO Unix NFS on the same hardware."