I wouldn't bother with the 5D II and its fixed pattern banding, the 5D III is good but doesn't have the 5D's look, and the 6D has the best image quality by far of those three but it's not the same look as the 5D, only the Mark II N has that look I know you want. The one advantage that you will see with the 5D Mark II or Mark III is improved image quality in low light. The 7D will look a little grainy, but the 5D will look significantly better, especially the Mark III. So, if you shoot a lot in the evenings, this might be something to consider. Good luck! – Matthew .

canon 6d mark ii vs 5d mark iv image quality