Don't know you personally (thank goodness...) but I bought the 6D as opposed to Nikon's similar FF offerings because I consider Canon's IQ to be superior. Bought an SL1 a couple months ago rather than the Nikon D3300 (i was able to compare the two) because I prefer the Canon's IQ. For people who look at actual photos rather than spec sheets, IQ is admittedly subjective, but I strongly prefer the look of Canon especially their ability to produce more pleasing colors. Also like their better contrast. In my opinion, the very poor color that I have seen with the Sony A7 models sample pics makes them rank even lower in IQ. I have noticed in reviews of the new Sony A7II that the reviewers consider the color dramatically improved. That may be a good sign for Sony, but just confirms how poor the color is in the original A7 models.
I wouldn't call color and contrast gimmicks.
Well, no, but are you referring to unprocessed RAW files (which are easily tweaked in software), camera-generated JPEGs (which can be adjusted in-camera by adjusting a vast array of color/tone/sharpness/contrast settings), camera-generated JPEGs at default settings, or something else?