SYS wrote in post #17545813
I had 40D and was looking to upgrade to 7DII. When it was taking too long for it to come out, I went ahead with 5DIII with the idea of either adding 7DII when it finally comes out or replacing 5DIII for it. When 7DII came out, it was a disappointment for me personally (got too used to 5DIII by then!), so now I'm thinking to just keep 5DIII and add whatever the next camera that'd improve on 7DII.
So then, are we to assume that your shooting is mainly of close or large objects, and that you are rarely focal-length-limited? That makes a huge difference when taking your assessment into account. I don't doubt that if you fill your frame in every case, the FF image has about the same (equivalence) or less (shallower DOF) noise, and that the same lens can resolve more lines on a larger sensor, but when people report better "IQ" in focal-length-limited situations vs the 7D2, I have to wonder if they are going by pixel sharpness (and pixel noise), which has no direct relation to subject detail.
By all measurements, the 7D2 has slightly less total noise, less banding, and more subject resolution than a 1.6x crop from the 5D3.
When I had a 7D and a 5D2, I only liked the 5D2 better when using the whole frame including shallower DOF. When I bought a 6D, I liked the 6D better in equivalence (less noise and banding noise), but preferred the 7D in good light, for focal-length-limited situations. Now with the 7D2, I find no advantage to 6D image quality in focal-length-limited situations, at all; the 7D2 has the best noise quality per unit of sensor area of any Canon DSLR, IMO, at both low and high ISOs. I only use the 6D when I want to shoot fast lenses wide open, or with wider FOVs not possible with the 7D2.