2 years ago was my first winter with my e90 330i. I did it without snow tires and am glad I did'nt wreck, came close a couple of times. Worst experience was on a relatively clean road (rt 59) going about 40mph then a patch of snow was plowed into the road , when I hit that spot the car did a mean fishtail and I almost lost control.
Last year I got snow tires and they were great for the snow. However, I blew 3 of the 4 snow tires during the winter on potholes in the city and bent 3 of my rims from my extra set. The runflats handle potholes much better. The ideal winter set for the city would be runflat snows. That is what I plan on doing this year. My e90 with winter set up grips better than my mini cooper (front wheel drive). This year I'll get a winter set for the Mini as well.
In short the e90 does much better with snow tires and feels more stable