Great Lakes - Chicago Commuter Bike

I'm currently looking for a bargain bike to get me through commuting during the Chicago winter. I've been a sort of "fair weather" commuter for a couple of years now and normally get to work (~20 mile round trip) on my Specialized Sequoia, but I would like to get something that can handle the snow, slush, and ice of a typical Chicago winter.

Would a mountain bike or hybrid be the best for this sort of thing? It would seem like the knobby tires on a mtn bike would give better traction. Would disc brakes be best? Anything else I should be looking for?

I'm looking around at Thrift stores, garage sales, CL, etc and trying to find a bargain. Any tips anyone could offer would be appreciated! Thanks!

I used a coaster brake cruiser during the winter. The brake works in any weather. Steel rusts, but so will aluminum in road salt. It came with fenders which are great for keeping salty slush off your back. The main drawbacks were the bearings were unsealed and the front wheel had no brake. Plus, it was slow. I am in the southwest suburbs.

If not that, then any bike with a disc or drum brake. When you get some slush on your rim, the brake doesn't work too well.

+1 ^
Rim brakes don't work very well in slush, and getting fenders will make your whole experience more pleasant.

The knobby tires of a mountain bike will definitely help with traction on wet/slushy roads compared to road bike wheels. Even mountain bike tires will lose traction over really thick slush or hardpack snow, though. If you find that you encounter that problem a lot, adding studded tires will help, though they will be overkill on most Chicago streets.