I had a 5D2 and 7D and sold them both to get a 5D3. Then I discovered I missed having 2 bodies so I eventually added another 7D to the 5D3. The 5D3 gets at least 80% of the use but I do like the 7D for wildlife and BIF shots if the lights good. Between the 6D, which has slightly better IQ and DR, and the 5D3 which has excellent IQ, a killer AF and is a fantastic allrounder I would go for the 5D3. I've had mine almost a year and it's by far the best camera I've ever had. I found it really easy to adapt to the 5D3 from the 7D and I find I can go from one to another without any major problems. The only problem I find is I keep trying to use the wrong button to pixel peep on the 5D3 (instead of the magnify and scroll).