I think it's a matter of perspective. When I first started photography, it was with manual focus film SLR. Back then, your focus aid was a focus prism in the center of the viewfinder (which actually was a good aid). When I moved to digital, it was with a 5D. At the time I found many things to like, but I did find its AF points limiting. For some tasks, I even preferred manual focus (so I got a 3rd party split prism screen for manual focus). When I upgraded to the 5D3, I was immediately struck by its improved AF system (and wasn't feeling hampered by its AF). I was already experienced with BBF and quickly adapted to the 5D3's interface for selecting points. I find the AF spread and interface on the 5D to be adequate for framing portraits or switching to AI-Servo for tracking shots. Since most of my tracking shots have been bicycle races, I've got my preferred tracking settings that give me a very high keeper rate. I take people's claims of focus accuracy with one or the other camera with a grain of salt, because it can differ depending on workflow. I get good accuracy with a Canon DSLR. Rantercsr mentioned Sony's eye tracking to be good for set it and forget it. Other potential advantages of sensor based focusing is AF spread that might go further out to the edges of the frame, and more AF points for tracking.