Just to add my two cents here:
I just ordered my m sport 335xi on the 7th of this month and I live in New Hampshire, where we have obviously bad winters. My choice was simple: dedicated winter tires and wheels for winter plus xdrive, plus not driving like an idiot, means i'll have no problems next winter. Then, come summer, I'll put my summers wheels and tires on and have a great sport sedan (i got the 6 MT) that for the daily driving I will do, will be more than fun...and...I still plan to mod mine with HRE wheels, coilovers, exhaust etc.
Obviously i'm spending some money here but the point is if you live in a bad winter area and plan to run winter wheels and tires that are separate than your summer set, why not go xdrive? I test drove a xdrive auto before I ordered and the thing handled like a dream...and I have driven my uncle's e90 335i 6MT so I had a something to measure the xdrive against.
Just my opinion....i personally don't think you can lose either way.
