Positives for the 1Dx:
2. Spot metering on any AF point (not just the center point).
3. A bit faster AF speed on most lenses.
4. better metering and AWB.
These are really very desirable features for reliable/pro shooting, esp. the af-linked spot plus RGB metering should do better in some situations where my 60d/6d becomes hit-or-miss and you have to expose for safety.Negatives about the 1Dx as compared to the 5D III:
4. No Magic Lantern: No raw video, no auto_iso with flash, no 15ev enhanced dynamic range, no focus stacking, no dof or automatic bracketing, no zebras, no raw histogram, no timelapses, no user scripting, no nothing really why I keep using Canon :-)
Btw for base iso stills shooting the 6d has arguably better iq than the 1dx: less banding, more dynamic range (out of the box and another +1/3ev with Magic Lantern's mini_iso module) which combined result in even more *usable* dr.11. Auto ISO upper limit above 1/200s (essential for sports if you use Auto ISO) - I sure hope Canon gives us this in a future 5DIII upgrade if nothing else. It cripples/crippled the Auto ISO feature and made/makes Canon look like idiots compared to Canon. Why Canon, why?
The answer is obvious, but this is an example of really braindead crippling that is only there to "upsell" customers. This problem is also fixed by ML which provides unlimited min. shutter speeds in auto_iso mode, 2/3 of my shots use this to get at least 1/500s (on 6d).the new auto exposure compensation when in Manual mode. Not really used it, but would have loved it when I photographed eagles last Nov.
Available through ML (though currently only in a "wip" module not yet in the nightlies).
damn when will all of that stuff get into a stable ML version for the 5Dmk3 I really want some of that and have they fixed the slow boot time. I dont want to install ML on my 5D3 unless its a more advanced stable release