The Samba server uses TCP to talk to the client. Thus if you are trying to see if it performs well, you should really compare it to programs that use the same protocol. The most readily available programs for file transfer that use TCP are ftp or another TCP-based SMB server.
If you want to test against something like an NT or Windows for Workgroups server, then you will have to disable all but TCP on either the client or server. Otherwise, you may well be using a totally different protocol (such as NetBEUI) and comparisons may not be valid.
Generally, you should find that Samba performs similarly to ftp at raw transfer speed. It should perform quite a bit faster than NFS, although this depends on your system.
Several people have done comparisons between Samba and Novell, NFS or Windows NT. In some cases Samba performed the best, in others the worst. I suspect the biggest factor is not Samba versus some other system, but the hardware and drivers used on the various systems. Given similar hardware, Samba should certainly be competitive in speed with other systems.