leslie, here you go.

ok, the manual wrx's come with a Viscous Coupling Locking Center Differential while the auto wrx's come with Variable Torque Distribution. this means that auto wrx's can be programmed to distribute power differently between the front and rear axles depending on what the driver selects. (this isn't standard...but i know a kid who is working on this...)

the manual wrx's awd system isn't capable of this because its simpler. now i'm not an expert on awd but i've talked to several wrx guys along with the owner of the autotrader (he drives a lancer evo5 and rally races in australia and new zealand) and they were able to explain this to me in limited detail.