Upload & Sell: Off
I sold my 5D Mark II and replaced it with a 6D late last year. The 6D definitely has better autofocus. The center point can focus in situations much, much, much, much, much darker than the 5D2.
Additionally, the outer points are quick and accurate in good light. (they start to struggle in low light, so I rely on the awesome center point in dark situations)
I don't use Servo mode much but in my experience the 6D has performed slightly better. I find that the 6D is quicker to adjust focus when the subject changes distance and I have less out of focus shots with the 6D (both in number and to the degree of out-of-focus-ness) compared to the older 5D2. However, you shouldn't buy the 6D based on this, as it's still not a great AF system for tracking moving subjects. Get the 5D3 if that is important to you.