You will notice more and more cars going all wheel. It only makes sense since traction is better cornering etc, not just in the bad weather. I have a 330xi. In a nasty snow storm we had here, it performed very well with just all seasons on. Using the hill descent is a hoot in really slippery snowy conditions. Since some of Vancouver BC is built on mountains we can have some steep inclines here; I've used the hill descent to advantage when other folks were afraid to go down the hill.
The DSC is really another system, like apples and oranges. In really snowy conditions going up a hill if the tires are spinning, you'll want to turn the DSC off or you'll find you can't get up it. I know its a tough call, lets make it a tougherl. If you can afford the 325xi, why not get the 330i.