<sigh />The D800 wins on megapickle count and the fact that, at ISO 100, you can push the shadows by four stops to get ISO 1600-equivalent noise whereas if you try that on the 5DIII you might get ISO 6400-equivalent noise in your pushed-four-stops shadows.
That's it? That's quite a lot. But in reality this discussion has occurred a million times since both cameras were released - and I guess we need to do it again.
The review posted by the OP isn't far off base. A lot of Canon loyalists - me being one of them - felt the 5D3 was more of a dot upgrade than a complete overhaul. I'm not complaining, but let's be frank, the 5D3 is really a 5D MarkII.2. The AF and burst upgrades are nice improvements, and the new ISOs are great, but there's no honest photographer who can say he's not
jealous of the D800's dynamic range and megapixel count. And for those who don't always need 36MP, the Nikon crop mode allows for shooting smaller sized files.
Many people try to argue, "hey - you don't need that DR or those MPs!" And for the average editorial, wedding, action, portrait and photojourn shooter, that's entirely true. And this is where I agree that the two bodies serve almost two separate classes of customer, 1) the wedding/portrait or general shooter, and 2) the studio or landscape shooter. Without a doubt the D800 has become the go to for serious landscape photographers or those looking to expand their commercial work in the studio. The megapixels are what editors and graphic designers are looking for in the commercial realm, and the DR and huge print sizes make landscapers giddy with joy. And in those regards, the 5D3 just cannot compete. No way, no how, so let's not pretend that it can.
That said, the wedding/event/portrait shooter doesn't need or want 36MP and that's where the 5D3 shines. I would never even consider taking a D800 on a event or wedding gig! Can you imaging trying to handle 800 36MP photo files in post? NO THANK YOU!
So each camera is incredible, and each serve their respective markets incredibly well. But to totally discount reviews because of our own Canon bias is a little silly. And besides, if we all weren't so jealous of the D800's capabilities, there wouldn't be rumors of Canon dropping a high MP body early next year.
Let's be adults and face the facts... Nikon caught Canon off guard with the D800. Canon is listening to its user base, and will respond accordingly. Just hold tight - we'll get our DR and MPs soon enough.