I7 3770k @4.9GHz 1.32v p95 26.6 small fft. Kraken x61. Silent mode 74°C. Performance mode 69°C. 5°C not worth the noise.
And that's the issue. Corsair in particular with older gen coolers slapped them with upto 2800rpm fans, extremely loud under heavy loads, even idle is @1800rpm at best. Yes, they perform quite well at that need, but if you don't need the 350w of cooling potential, like your OC or stock cpu is only pushing 200w at best, then a larger air cooler works just as well, and in the case of Noctua, beQuiet and Scythe and a few others, much quieter. And this coming from an aio preference. One of the single best AIO's was the Corsair H105, even with stock fans, it out performed the h100i v2 in every way.
Fans make all the difference with AIO's. There's huge differences in fan design that are not seen by the cfm or sp numbers. Many case fans with huge cfm, only do so with an extremely broad cone, great for massive air introduction, lousy for rads, and others like the NF-F12 from Noctua, with relatively small cfm are straight cone, so all that air is condensed directly in front, going straight through a radiator, not causing massive turbulence and little actual airflow.
There's also differences in radiator fin spacing, tight packed fins do better with higher sp fans, loose packed do better with higher cfm fans.
There's also differences in ability. As good as the NH-D15 or h100i v2 are at lower wattage output, neither one can handle the high wattage levels from extreme OC or uber high/heavy thread usage.
So it's all a matter of degree, need, ability etc. The h80i comes in at almost identical performance to the h100i v2, until the wattage is close to the h80i max, the h100i v2 has a higher ability and dusts it handily. Same as a H105 is equitable to a h100i v2, until max.
And all that can change with case airflow, airflow restrictions, placement of the radiator, gpu heat, push or pull etc.