Why do people take any of Andrews words seriously?
Andrew says "I also did some research on XAVC-S. It records in MP4 format but perhaps rather disturbingly it has a much lower bitrate than the GH4′s 4K codec. It is just 60Mbit/s vs 100Mbit/s on the GH4 in Ultra HD." He did his research eh?.
Then explain the Sony FDR-AX1's 150M/bit XAVC-S in which a 1 minute research would find and I quote, "In order to provide 4K video recording in a consumer model, Sony designed the FDR-AX1 to support the XAVC-S 4K/HD recording format which is usually reserved for professional applications. However, since the XAVC-S codec will save as an MP4 wrapper, you can still create web-friendly videos that can be easily shared on social media sites like YouTube. Another highlight of the XAVC-S recording format is its ability to record images at 150 Mbps in 4K".
Seriously, do your homework Andrew.