The 6D and 7D2 have the same megapixels - 20.2,
the focal length is pretty much the same: 6D @ 600 , 7D2 @ 400*1.6 crop = 640
and I see that zooming in to 100% causes nearly identical photos.
With respect to what I made bold and red, I am not seeing what you are seeing.
The image on the left looks way, way, WAY clearer and sharper than the one on the right. . The feather detail is SO MUCH crisper. . It is an enormous difference in image quality, not a subtle or slight difference.