[Alpine TSi]

From what I am told 4WD vehicles don't put power to all four wheels at the same time. Typically it is only like your front driver and rear passenger wheels getting force. Only when the car senses that either of those two wheels are slipping, then power goes to all four to pull it out. Now another common misconception is that 4WD will save your ass, not always true. Most 4WD vehicles can't fully operate that system over 45 mph and will only continue to be a diagonally driven 2WD vehicle, even under a slipping conditions. Now new Silverados and such have made their systems capable of this at any speed.
So in reality you want an AWD system over 4WD, and this is why I see a bunch of housewives in their pre '03 Tahoes and Expeditions in the ditch during winter.. Ha serves them right...

Now this is just what I have been told and kind of know, don't quote me...