* ff has more leverage for postprocessing, this is what matters the most to me. If you try to raise one color channel on a gradient (say lessen or intensify blue on a partly cloudy sky) the crop shot will immediately fall apart while the bigger ff pixels allow for more postprocessing creativity or fixing.
This is true but an exaggeration. Crop images do not 'immediately fall apart.' You have to push to see the difference.
Also the ff has less problems on the red color channel on plain surfaces, a known issue with Canon sensors, try shooting a red mushroom if you don't know what I'm talking about.
This is true at anything other then the lowest ISOs. But it's true for most (all?) crop sensors, and even the FF ones as the ISOs climb. You just have more ISOs where red doesn't suck on FF.
In reality, I find the ff has a 2-3 stop advantage over crop because with crop iso800 is the highest "safe" setting while with the 6d it's iso6400, and truth to be told I'd still prefer the latter if the dr is low.
The crop sensors are fine to about 3200, though I agree that Canon's FF sensors are 2+ stops better at high ISO.
* Viewfinder: Not directly sensor-iq related and last, but not least - the more expensive crop cameras have an somewhat ok vf, but with ff you see more of what you're shooting due to the larger mirror which is a reason for ff on its own as in "iq for your eye".
I don't notice a significant difference vs. the 7D, though what you say is true for the other crop models.
and of course for tele shots with 300mm * 1.6x crop factor which makes a decisive difference for wildlife.
It's hard to beat a "built in" 1.6x teleconverter