At a per megapixel level the Canon 5D Mark III sensor is sharper than the D800 and with the lens line up Canon sensor manages to get the best out of the lenses compared to the Nikon!
Finally some good news
http://www.dxomark.com/index.php/Publications/DxOMark-Reviews/Which-lenses-should-you-choose-for-your-Canon-EOS-5D-Mark-III/Canon-EOS-5D-Mark-III-vs.-Nikon-D800-Competition-is-closer-than-expected
Finally some good news
http://www.dxomark.com/index.php/Publications/DxOMark-Reviews/Which-lenses-should-you-choose-for-your-Canon-EOS-5D-Mark-III/Canon-EOS-5D-Mark-III-vs.-Nikon-D800-Competition-is-closer-than-expected