As somebody with no 'axe to grind' (I don't have a D4 or D800), I see the D4 as better. The ability to disregard the consequences of boosting the ISO to an extent undreamed of even 4 years ago outweighs the higher Mp of the D800. As people have been saying for a while now "I want usable Mp not more Mp". The 16Mp of the D4 do seem somehow 'finer' than the 16Mp of my D7000 - maybe I should have said 'less apparent'.
The price is crazy though so I will be super content with a D800 one day. Don't get me wrong here, the high ISO performance of the D800 is great, it is just that it looks to me like the D4 is better.