True, cpu to cooler fluid transmission is better with water.
And cooling air throughput is essential.
But, then the fluid needs to be cooled by passing through the aio radiator/s.
The efficiency of that process is similar to the efficiency of an air cooler transferring heat from the cooling fluid to the cooling fins of the air cooler.
A simple air cooler with a 120mm fan is going to be about as effective as a 120 aio.
Similarly modern dual tower air coolers like Noctua NH-D15s have about the same radiator capability as a 240 aio and will cool similarly.
One complication is in mounting a aio radiator.
If you mount it to take in cool outside air, the cpu will be cooled best. But the heated air will enter the case and motherboard and graphics card cooling will be impacted.
If you mount a radiator to exhaust air, the radiator will not be as good for cpu cooling because it has heated motherboard/gpu air to deal with.
It is a catch 22 situation.
With an air cooler, it is simple.
Fresh air comes in the front, flows through the cpu cooler, motherboard and graphics card. Then exits the case directly, taking component heat with it.
Also, aio coolers have a more limited lifetime.
The pumps are mechanical and in time, they will wear and lose efficiency.
The liquid can acquire contaminants blocking coolant flow.
Or coolant can leak. While rare, a aio leak can have disastrous results.
Did anybody mention that air coolers are usually cheaper?