You'd be a better judge of the IQ of them than me since I don't shoot Nikon & likely won't unless they start making lenses to meet my needs (no lenses of the same quality as the older 35-350 L, 100-400 L IS or 28-300 L IS) so although IQ is a factor in deciding what to buy so is the rest of the system of parts needed such as lenses, strobes etc. Also be advised that many sites cater to their sponsors (advertisers) when doing reviews so one has to really know all of the testing methods used to be sure they are as identical as possible BUT since you can't swap the lenses between the different bodies an important part of the test may effect the results.
I'll assume you're comparing Jpg's rather than processed RAW files and that's another variable because every manufacturer tweaks their software to produce images that THEY find pleasing. Some prefer stronger greens, others prefer nicer skin tones, or nicer blues for the sky etc. Also note that you can set some of those parameters in your menu system, but I doubt many do. You can change sharpening & saturation, brightness & contrast very easily & experiment to see what's more pleasing to YOU.
I've borrowed this from the signature of a member of another photography forum I belong to & strongly suspect it's an accurate quote but I haven't verified that.
"If you aren't getting extraordinary images from today's dSLRs, regardless of brand, it's not the camera!" - Bill Fortney, Nikon Corp.
"A skill is developed through constant practice with a passion to improve, not bought."
