I might upgrade from my 60D with 17-55 f/2.8 to a full frame 6D with 24-105L. While browsing the internet, I found out that a lot of people complain about this combo because there is something wrong in the 6D when using the lens...like the lens doesn't seem to be as sharp as when using it with 5dMKII or 5dMKIII. I find it odd...but I am here asking you guys to confirm me that is can't be really true???
Or....should I buy a used 5dMKII instead a new 6D ? will it be a good improvement over my 60D in terms of image quality?