I just pre-ordered the 6D2 from B&H. I have been shooting with the 6D1 for the past 5 years and have liked it very much. I wavered between the 6D2 and 5D4, but after reading the final specs and a couple of preliminary reviews, I chose the 6D2. Like you, the AF was a principal driver in the desire to upgrade, along with a bit more resolution for cropping. As far as the comparison with the 5D4, some of the considerations were these:
1. The AF with 45 cross points should be adequate for my shooting. I do wish they were not all condensed toward the center of the frame, which somewhat defeats the purpose. But, ok.
2. Not often, if ever, will I be able to detect the difference between the 26 vs. 30 megapixels.
3. 6.5 fps exceeded my expectations and is only .5 less than the 5D4.
4. The 6D2 AF will function with the 1.4x extender as well as the 5D4.
5. I don't use video, so the 4K of the 5D4 was immaterial.
6. I am eager to have the articulating LCD for LiveView as I get older and less flexible. I think that was a flawed omission by Canon on the 5D4 and was a strong consideration for me.
7. I don't care about 2 card slots.
8. Low light shooting should be about the same, both for IQ and AF.
9. I am already familiar with the simpler 6D functions and it's doubtful that I will use several of the more sophisticated features of the 5D4.
10. While I don't shoot in rough weather, and thought the better sealing of the 5D4 would not be that important, I was nevertheless glad to see that Canon significantly upgraded the weatherproofing of the 6D2.
You can't go wrong with either choice, and you're going to be delighted with your new camera. The $1,000 difference in price wasn't a big consideration for me, but the savings will help me rationalize succumbing to my next GAS attack.