My Pirellis SUUUUUUUUUCKED even when it was a little moist out. Doesn't help that we have 400+ horsepower. My previous Camaro, the winter before last, I think, got stuck on a hill when we had snow. I couldn't drive it home, so I had to back it into a parking lot and leave it there overnight. :( I never replaced the tires on that one.
This time, I got my Conti DWS and never looked back! They are seriously amazing. The Pirellis would even break loose in the dry occasionally, but they were getting low on tread by the time I replaced them. It's almost scary how well the DWS stick. Do it!