my understanding is that a recirc is quieter. and therefore more to the taste of non-petrol heads.
a dump valve to atmosphere i think may technically have less resistance to the action of dumping, and would also avoid introducing air already worked by the turbo back into the inlet.
as for WRC, they use a different system that you wouldnt want on a road car unless you want to change the turbo every few weeks.
i believe they run anti-lag systems, so that the turbo doesnt slow down when changing gears. you get a funny squeeling sound which i think is something to do with the turbo as it continues to spin but the engine momuntarily is not using this charged air.
technically any air dumped is effort wasted, so from a performance point of view WRC cars avoid this. However when you consider what a DV does, its there for reliability, which IS something you want on a road car.
im sure someone will give you a more scientific answer shortly.