It seems to me that the noise level of 7D is higher than that of 5D2. I took the 7D out for a shoot yesterday. All were done at ISO400. On viewing the images in LR2, they seem grainier than I will expect at 400 at 100% crop. For the 5D2, noise will start to creep out at 800 or more.
But I just read in the 7D manual that : if the 'Auto Image Optimizer' function is enabled (factory setting is enabled and set to standard) it may increase the noise level in the images taken. So, I will probably have turned it off an try again...
Just an observation, nothing scientific about it too