Upload & Sell: Off
That statement seems to be the exact opposite of everything that I've read about the 6D. Low light focus on the 6D is supposed to be a big advantage. Try these:
Many amatuers are selling their 7Ds to buy 5D3s but that doesn't make the 7D a bad buy at the moment. It's a great camera at an excellent price right now.
I have the 7D and 6D. In my experience, the 6D does focus much better in low light but the 7D is head and shoulders above the 6D for action shots in reasonable light. I'm planning to get a 5D3 soon and am on the fence on whether to keep the 7D for a 2nd backup as well as shots where I'm focal length limited.
The 7D is not a perfect camera but in reasonable lighting, it does a great job.