c_h: Whichever way you go, suggest you make sure you have room to mount studded tires. I did this past winter a little north of you (Herndon) with a cross-style bike & 700x35 studded tires. Missed a couple of days with the major business closures and I think I drove a few times, otherwise rode thru it. There were 1 or 2 days after the big snows where I would have liked an MTB with really low pressure tires. That might have made dealing with the slush piles on the roads a bit easier. The 700x35s were fantastic on icy and packed snow areas, but sketchy on soft stuff (front wheel tended to get knocked askew). I had a 2nd set of wheels with 700x32s mounted when I didn't need studs or got tired of listening to the tire knobs on pavement. One more thing - fenders rule!

If you think we will have another winter like 2009-10, I'd probably go with an MTB just to get better riding in snow. If a more typical winter, I think a cross or touring style bike that can take wider/studded tires is fine.