Professional Sports/journalism/wildlife: 1D X
Professional Studio/portrait/landscape: 1Ds Mark III
Professional Weddings/multipurpose camera: 5D Mark III
Amateur Sports/wildlife or for a Pro instead of a TC: 7D
Amateur Portrait/Landscape: 6D
If you want to lock the focus in extreme low light:
1. choice: 1D X
2. choice: 5D Mark III
The 1D X and 5D Mark III can lock the focus in low light while the 6D is giving up.
Outer focus points, yes. Center, no. Enough of these "amateur" categories. A lot of professionals were shooting and still are shooting with 5D2 which we can say is beaten/on par on almost all camera features by 6D. I'm sorry but I disagree with you when you put 6D as an amateur camera. I can even remember when all cameras were still using MF and yet those cameras were not considered amateur by anybody.