The differences I've noticed between D4 and 1DX is the high ISO noise reduction and printing capabilities. The other issue is that I cannot compare which camera locked focus more times, because I have never had my 1DX not lock focus. If you are in such poor lighting that you need to set your shutter that low, aperture that wide, and ISO that high, then who really cares? Why would you even shoot in that situation and expect anything more? No camera in the world will AF very well, so you cannot say it's just the 1DX. The D4 misses just as much. Even in the darkest sports venues, I can easily shoot at 1/640s, f/2.8, and ISO 6400 on a 1DX, and not underexpose. The beautful thing is that if I do EC, I can raise the ISO to 10,000, apply 50% NR, and print a beautiful 8 x 10. If I have to go darker than that, I won't shoot or I'll use a flash.
When you say your D800E locked more times than your 1DX, did you have both at the same time alternating each camera? Was anyone in this thread shooting with both at the same time at the same event, one in each hand?
Why in every other thread "the camera doesn't matter" unless it's a Nikon vs. Canon issue, when there's a problem, suddenly it's the camera again? Oh you guys keep me so entertained on this site. Keep it up! Meanwhile I'm going to keep shooting with my 1DX's.