Drifting slightly off-topic, I have spent many interested hours this evening on that "Comparometer".
Two more interesting comparisons vs. the 5D3:
1) Pentax 645D : It only goes up to ISO1600, and at that setting it is WAY more noisy than the 5D3. On the other hand, of course, the Pentax destroys the 5D3 for resolution. (Captain Obvious!) At ISO100, the Pentax is stunning, as you'd expect.
2) Leica M9 : Perhaps not a fair comparison, since the M9 is a few years old now. It is destroyed by the 5D3 at low and high ISO. Even at ISO200, the Leica looks way noisier than the 5D3 and the Leica's reds are even more deficient than those of the Canon. Greens seem about the same; perhaps Leica wins in the blues. But it's very subjective, I suspect.
I could spend hours on that site! (Oh, I just have!)