I think that I will go with the Nikon D5 for now (try it out before committing the full $6.5K or even $6K on the 1Dx Mark II). Why?
Dual XQD or dual CF slots, 153 autofocus points w/99 cross-type, and over 3 million ISO (which means a higher native ISO of 102,000 - so in this case, double that of the 1Dx MII which is at 51,000) with the
same resolution sensor (Nikon slightly larger at 20.8 vs 20.2 :

). Cleaner base ISOs across the board AND -4EV across the board. Additionally, Nikon does not play with the dynamic range. They already have it. ~4,000 clicks per battery. A great feature that is also present in the D810 battery. 200 continuous RAW files per burst at 14bit uncompressed (vs. Canon's 170 continuous burst) even though that Canon has an extra 2fps (not a big deal for me here).
I care about the image quality and telling a visual story with better capabilities, especially in darker environments with less noise.
* Regarding the metering, the D5 has a 180K pixel RGB metering system and Advanced Scene Recognition System with group AF (finally). Honestly, I do not know how this will compare to the 1Dx Mark II's 360K pixel RGB metering system. I already have experienced the wonderful iTR AF system of Canon on the 7D MII.
Nikon says that it drastically improved performance for sports and movement. Let's try the camera out first and find out. If it does not meet my expectations, then I will return it and adopt the 1Dx Mark II.
**Overall, I don't care about the video. There are already other professional tools that do wide DR / custom cine profiles, and 4:2:2 or higher for a proper professional looking output. I don't want the typical DSLR video (rolling shutter, 8bit compressed image with no alteration on controlling DR on the shadows or blacks).
Different job, different tool.