5D Mark III raw compared the 6D in ACR 7.3
I did the same thing and noticed the same difference between the 5D MkIII images and the 6D. However, I wouldn't put too much stock in differences in sharpness. The slightest bit of difference in focusing at this distance will make a big difference. For instance, if you look at the D600 images versus the 5D images, they have similar sharpness. However, if you look at the dpreview studio images, the 5D MkIII images are noticeably sharper than the D600 images (comparing RAWs processed by LR4). I think this is the reason Dpreview will be altering their studio setup in the future in order to minimize depth of field and focusing differences. Anyways, that's a nice showing by the 6D. I will be very interested in reports of real world AF performance of the 6D.