Having bought a D800 (not E), it is certainly true that the files are much larger, and resolution is much higher. I also bought the Nikon 24-70mm f/2.8G and a Nikon 200-400.
However, when I looked at the more expensive Nikon 24-120 versus the much less expensive Canon 24-105mmL, and the Nikon 80-400mm versus the older but much better Canon 100-400mmL, and then Nikon has nothing the equal of my 135mmL. I just sold the camera and lenses and kept on with Canon.
Lenses are where the investment is, Camera bodies last 3-4 years before being updated, so I have a much larger investment in Canon lenses.
One additional thing. While my D800 was wonderful at ISO 100 and even 400, it started rapidly gaining noise at ISO 800, and at the very high ISO's 6400 and above, its DR advantage turns into a negative.
The other issue is post processing hundreds or thousands of images when it can take 6-10 times as long for my fairly powerful computer to render a image, or to grind out Noise Reduction.
I'd easily recommend a D800 to someone using it for low ISO landscape images when they only took a few at a time, but not for someone who uses it in very low light and shoots 500 or more images a night at ISO 6400 or above.
Its merely a matter of the best tool for the job.