Why not get the X-drive and upgrade the suspension? That is the route I am going. I had a 328i RWD w/snows last year, it was manageable, but my Subaru w/all seasons runs circles around it (so much for the AWD/all seasons <RWD/snow tires talk on here) I am at the mountain 2-4 days a week to ski and teach, and we get an average of 400 inches/year there. Here in town, a lean year can be 30 inches, a big year 100 inches. The RWD works OK, but you have to pay attention, you have to watch your RPM's to keep torque at a minimum, and use really good snow tires. The AWD is much better in snow, and if it snows 6 inches during my ski day, I know I will be able to get out of the parking lot: that would be tough in the RWD. Honestly, most people griping about the AWD cars are probably feeling the sluggish handling (due to crappy 4x4 suspension) more than they are the drive system. It weighs a couple hundred pounds more in a 3600 pound car: that is what, 6%? People are pushing an (often tuned) N55 engine that hard in daily driving that they are worried about, much less can feel, a 6% weight increase? Sure, if you are tracking it, but.....
The X-drive is still RWD biased, and with so much power in the N55 (especially if tuned), you can even get the rear tires starting to come loose in cornering before the AWD kicks in.
So, if you need the X-drive, set aside $1600 for a set of coil-overs and install, and call it good. Best of both worlds.
I agree though, if you don't need AWD, then get the RWD setup. Gets a couple of MPG better, is a lighter less complex car. It is what I would have if I didn't live in the mountains. If I only occasionally saw snow and lived in a pan-flat area (as most of the posters who live in the Midwest do), then it would change the equation as well. But, when you have to regularly drive up to 6500 feet elevation in the PNW in the winter, or up to Snowbird/Alta, considerations are different.