This is simply not true in my experience (and I own both). After more than 100,000 images out from the 7D, the noise is very poor. Anything over 800 is just simply bad. My two most popular images were both shot (unfortunately) at ISO 800 on my 7D and I'm not comfortable printing them anywhere over 12"x18". This is with thoughtful and deliberate noise reduction in post. My 6D is really clean, I couldn't be happier. No noise reduction is even needed at 100, and ISO 1600 is much cleaner than the 7D at 800. I can't wait to ditch the 7D.
your experience mirrors mine. canon really hosed us when they ditched 1.3 crop.