AWD is nice, but not a must. At least in Central Ohio, most of the major roadways are clear within a day or two to make the added benefit of AWD not necessary. I drove my 528i with no issues in winter and heavy snows.
I have an Audi A4 Quattro which is absolutely brilliant on snow. The biggest draw backs to an AWD car is the fuel economy. Expect about 2-3 less mpg and slightly less acceleration. But, it is amazing when you can drive your car though 15" of unplowed snow on all seasons without getting stuck!
Based on my experience, my preference would most to go with the RWD car whenever it is an possible, then AWD, and regretfully FWD if it is the only option.