Nikon D800 (left) and Nikon D4 (right) sample images side by side
As you can see above, the D800 image contains significantly more data. In good light and with good technique, the D800 offers a significant cropping advantage over the D4, and this can't be disregarded for wildlife. Of course, occasions where a wildlife photographer finds good light and perfect conditions are few and far between, so the D800 won't win this fight that easily even in terms of image quality! I'll be posting more comparison articles over the next few weeks, dealing with areas like noise and ergonomics.
Links to the original images are below; I've exported them directly from the RAW files using Lightroom with no sharpening or any other changes. Please feel free to check them out and share your own thoughts at the bottom of this page. Thanks!
Sample image from Nikon D4
Sample image from Nikon D800