PS I think the Porsche AWD system is actually pretty advanced, was just talking out of my bellybutton before.
Why the WRX is somewhat optimized for rough roads:
When they first started building the WRX, WRC was contested by Group A cars. In Group A, if you wanted to race with an AWD turbo car with a 2.0 l motor, you had to build 10,000 of them. So cars like the WRX and Mistubishi Lancer Evo and Lancia Delta Integrale and Cosworth Escort and Mazda 323GTX came into being. You couldn't change the bodywork or suspension geometry or any major dimension of the car, so the street cars were laid out with a configuration that would work pretty well in the WRC.
Since then they have added a new class (WRC cars) which is run in addition to Group A. WRC cars are allowed much greater changes from the stock homolgated cars bring them up to rally spec. So you see cars like the Peugeot 206 (which is a FWD 1.6 l normally aspirated dog in road-going form) which get to add in a full race 2.0 l turbo motor and AWD drivetrain and optimized suspension which makes them able to compete with the Group A cars. Same for the Hyundai Accent or the Citroen Xsara or the Ford Focus. The manufacturers no longer have to build high performance homologation specials in order to be competitive in WRC.
But Mitsubishi and Subaru have stuck with their old platforms, because the road cars have been sales successes, and were still competitive in WRC. Also the cars retained their homologation for lower FIA classes (Group N) where they are dominant. Group N is great, because the cars have to be very close to stock and there are hundreds (thousands?) of entrants, which means there are tons of racing parts available for us ricers which will bolt right on to a stock car.
The WRC class cars are starting to kick some butt though. Subaru made a slight change with the GDA Impreza (you'll notice the WRC fenders are a little wider than the road car), but Mitsubishi stuck with the Group A car. They both did well at first, but the WRC class cars have come on strong, and Subaru and Mitsubishi have only won a couple of rallies since 2001. I think they both might have to come up with a smaller car to run with Peugeot and Citroen and Ford who are basically stuffing full race chassis into very small econo-hatches.
