OK, things I learned in the snow today.
1. Front undercarriage cover + > 6" snow = floating front wheels, AKA no turny well.
2. Big straight exhaust hanging down in > 6" snow = resistance + acts like a keel, AKA no turny well.
3. Wicked fast road course/autocross suspension < optimal in uneven snow/icy conditions
4. Hankook W300s work great when actually in contact with snow.
5. Sumitomo HTR+s work great in deep snow. (A4, same size as WRX, 225/45-17)
6. A4 + Sport suspension + HTR+s > WRX + 12.2/11.6K springs + W300s > All SUVs in 6"+ of snow.
The funniest part was blowing past a SUV spinning tires and sliding backwards while trying to go up a hill in my neighborhood. If he hadn't sstarted to make progress, I had a tow strap in the car, and was going to offer him a pull.
Also, the W300s have great ice grip. Watching other cars and SUVs slip sidways, or not be able to start from a dead stop on ice was quite amusing while I had could easily brake, launch, an turn on it.