I would expect better performance with those, especially since it looks like you're transferring large files, though like mentioned it will never be close to disk speed, maybe 50/60MB/s at best, I believe the plugin uses rsync internally for the transfers, but never tested myself, you could try for example with midnight commander (mc on the console) to compare, but note that it would be much faster transferring to a pool or an unassigned device then transferring back to the array with turbo write enable, I always try to plan things to avoid internal transfers in the array.