Mark at Village Voice offered this comment:
“I did study the advantages of XAVC compared to the AVCHD : let’s say that XAVC shoots @46/47mbps while the AVCHD goes down to 28. But I can’t see any difference (after comparing frame by frame for one entire evening). No difference even grading the colors (one is 10bit and the other 8bit). The difference is about the file size, and if you use catalyst prepare/browse (that nonsense mandatory to produce anything in XAVC) the size becomes ridiculous (5times bigger.. something like that). Broadcast was fine with the 35mbps of the EX1 and is fine with the 28mbps of the X70 in AVCHD. Unless you go live but in that case the output will be SDI , or interlaced.”
As a note, Mark’s assessment was based on comparing XAVC and AVCHD for HD output. This was before 4K was made available for the X70.
Now that 4K is available, use of XAVC is mandatory, so even if you’re still out-putting to HD–as most of us will be–the advantage becomes 400% greater information available in every frame. This should (and per reports does) improve your HD quality, but also it now allows you to crop any frame as much as 400% without any loss of quality–a real boon for editors.