[Stuart W]

The answer is in the question

FTP stands for "File Transfer Protocol" which is a protocol specifically written to transfer files.

SMB stands for "Server Message Block" which is protocol written to do a number of tasks, like broadcasting share information as well as transfer files.

This means FTP will usually be the fastest method to transfer files over an IP network simply because that is all it was created to do.
As well as this, SMB is also using up bandwidth by polling for other SMB info on the network and broadcasting share information.

HTH