It depends what you mean by "fastest".
Non-CF network access means FTP, and that will achieve the greatest throughput (but the recordings will not be decrypted in the process, they will need prior decryption to be of any use).
With the CF there are a couple more options: install samba and you can use a Windows computer through the normal Explorer interface to move files around - same reservations about encryption though. The WebIF media browser offers a download option in the media browser, and this will also decrypt on the fly if required (but it slows things down a little).
Either of these network options run at similar speeds, and if you want to know what the speed is you had best run a trial and measure it.
However, with multi-gigabyte files nothing goes terribly quickly. I rate "fastest" as "the least imposition on my time", so actually I prefer to do a bulk copy to a USB drive (which decrypts if necessary) which can proceed unattended, then walk the USB drive to my computer where it copies much faster and ties up the computer less than running a network transfer.