I recently completed a project shooting test footage with the F3 to compare S-LOG vs. Cinegammas and many different codecs. I recorded to SxS cards, NanoFlash, Ki Pro Mini, Pix 240, Gemini 4:4:4, and a Cinedeck Extreme covering most flavors of ProRes, DnxHD, DPX, XDCAM, CineForm, and more.
If this is a topic that interests you, it might be worth it to order a copy of the footage before spending thousands of dollars on upgrades and accessories. The footage is unedited, unprocessed, camera-original clips. Most people could never do this testing on their own, and why listen to the opinions of other people when you can come to your own conclusions about the relative value of S-LOG and external recorders?