BinaryNights, creator of [ForkLift](https://binarynights.com/), did a comprehensive speed test of all of the major FTP clients for Mac. Taking into account that this was performed by the developer of one of the apps, they go into solid detail about the testing procedure and parameters, and the results are presumably verifiable. And, as I would have guessed, in most cases every client except for Cyberduck performed pretty closely, but with some surprises in handling multiple-file transfers.
