According to the 6D manual, AF points are selectable by using both wheels to move the AF point both vertically and horizontally to the desired position. Yes, the joystick is nice, but you still have this option; which may be faster.
Funny how the mind works...
Before the 6D, I had decided that investing in a 5Dmk3 Kit would be out of the question until I start (hopefully) earning a bit more than crumbs from my productions. After first getting overly exited about the 6D and then slightly disappointed, I find myself much more prone to pull the trigger on the mk3
I think you may have misread my review (or I wasn't very clear). The 5D IIIs AF is excellent and fast in all situations - including low light. Very low light is obviously more of a challenge but mostly it locks fine. The 6D however has a slightly better centre point in near darkness - it locks a bit quicker and doesn't seem to hunt at all (yet).