Subaru's AWD is permanently on 50front/50rear at all speeds, except for WRX STi, where you can change the torque split on the move between 50front/50rear to 35front/65rear.
Most passenger cars meant for slippery tarmac or dirt / gravel track use (WRC conditions) like the Impreza, Evo, Audi Quattro, etc. will use AWD systems. Most "real" offroad cars like Landrover Defender, Toyota Landcruiser, Mitsubishi Pajero, etc. will use 4WD systems.
The main difference is in the type of differentials used. The differential system transfers torque to the wheels which are not slipping, relative to each other. In real offroading situations, you will need differentials which can fully "lock" the torque to be transmitted to the non-slipping wheels, meaning, if one wheel is slipping, then 100% of the torque goes to the other 3 wheels. You can see this in operation during serious very slow speed 'camel trophy' situations in the jungle. Most manufacturers call these systems 4WD.
In WRC-like conditions, the cars will be racing on tarmac, dirt or gravel tracks or snow, which is still very fast, but very rough or slippery. These kind of situations dont need differentials which can fully "lock" the torque, but is actually faster for the car to shift only part of the power from wheel to wheel as required. Most manufacturers call these systems AWD.
For example, the WRX STi has 3 viscous coupling differentials (front, centre and rear) which does exactly that.
