Different coolers will have different cooling capacities. Some higher-end air coolers on the market can outperform AIOs, but an AIO can usually handle major fluctuations in temperature a lot better due to the thermal properties of the coolant and how the heat is moved away from the source (to the radiator from the CPU) for cooling. There are a lot of factors that would have to remain constant, including the variability between units and the same situations, to do an accurate comparison between the coolers.