With all due respect, you seem to be repeatedly making this point in a variety of threads, but without substantiating it. You also don't seem to own any full frame Canon camera body according to your signature, so where is the source for your information?
Asking for sources is perfectly fine - though since this is not a scientific article, skipping them unless asked to is imho also ok. While looking for the adequate ff camera (5d2/5d3/6d) I did a lot of research and downloaded multiple raw comparisons and had a look for myself in Lightroom. What exact source are you asking for - that the 5d2 is sharpest at low iso, or that the 6d is less sharp than the 5d3? If I can I'll try to post where I got the information from, though it were a lot of articles so I'll really have to look. Not to be misunderstood: I also think the 6d iq is overall much better than the 5d2, that's why I'll buy the 6d.
Btw: I'm not a big fan of the "you don't own that gear, you can't tell anything about it" argument - I for one never told it to anyone commenting on, bashing, praising or comparing the 60d w/o owning it. While it is certainly true that ownership or extended rental is required for evaluating gear handling over longer periods of time, your 6d probably has the same sensor as any reviewer's 6d, so I'm confident I can come to valid conclusion when using other people's raw files. If reading sources would be no viably way to acquire information, scientific or journalistic work would be confronted with quite a problem.