Another advantage of the pullies is that they slow down the water pump, preventing cavitation at high RPMs that could lead to overheating with sustained high rev driving like on a road course. This applies to the DE, but I'm not sure about a VE.
Then there is the issue about whether a light pulley reduces engine life on a VE because of the crankshaft configuration (fewer counterweights). Passionate arguments have been offered on both sides of this question.
I agree with TheSnail, however, installing a crank and water pump pulley is not something that will make a perceptible difference to the driver. However, installing a lightened flywheel will make a very perceptable difference in acceleration, especially in the lower gears. IMHO, the flywheel is a better bang for the buck.
Sorry, Daveracer, I know you didn't ask about flywheels.