It's interesting you see that much difference in them to rate the D4 that much better, I see they are different, but struggle to say one is better, both are a bit plasticized by the noise reduction, to me the D800 shadow detail held up a bit better even.
But remember these are hardly scientific, while under the same lights at the same stadium, they were 4 months apart, and 1:1 is not how anyone looks at photos anyway. It was more curiosity. The overall set is maybe a better comparison.
As to the question about difference in exposure, I'm on the road today and can't do the math, but they are pretty close (it's shown on the top of each image), e.g. 2.8 vs. 4 but 1/750th vs. 1/400th, ISO 2800 vs. 2500. I did look last night and neither had any exposure compensation added in post.
Again, not scientific, was partly fascinated that I was so close to the same image number at the same event four months later and found a shot so similar.