That is not entirely true.
A good W2A system is well capable to dissipate continuously. The dissipation depends on the radiator, and if the radiator is of the sufficient size (eg stock ST205 is plenty sufficient), it will dissipate continously.
Although W2A system will run slightly hotter, the temperature will be more consistent, as well as W2A system has higher capacity to buffer the spikes than normal A2A system. It takes much more energy to saturate 1 kg of water versus 1 kg of aluminium, you also get a lot more water in W2A than aluminium in A2A.
The aluminium to water transition is more conductive than aluminium to air. You could have a lot greater surface area on the radiator, without having to deal with lag on the W2A system.
There are many advantages in W2A system for all uses, except perhaps in situations where there is continuous air flow over the intercooler.
The main disadvantages in W2A system are:
1) Cost
2) Weight
3) Complexity
The advantages are:
1) Efficiency
2) Consistency
3) Lag