That is two very different cameras. The 6D has big issues with aliasing, but has a large sensor. Bmpcc has very little aliasing, but a small sensor. So the images out of the cameras are quite different. My opinion is that there is no point to debating which is better when two options render vastly different images.
Secondly the bmpcc shoots 10bit log prores which to me is more convent than raw while providing great images. I was shooting raw on the 5DmkII back in the day, I never liked the converting steps, huge files and crazy aliasing. So I prefer bmpcc 10bit prores over canon 5DmkII/6D raw. On the 5DmkIII, where the aliasing is less of an issue, perhaps other conclusions would be drawn.