I completely get the traction vs. handling debate. The thing with a Boxster in snow (with snow tires), it that does fine for daily use. In the daily winter driving conditions you'll face in most of the US your going to face 1-2" of snow, mostly plowed roads, and the occasional storm.
The Boxster does just fine in those conditions. Now if you want to go driving in 4+" of unplowed snow you need a Jeep. It may not be as good as an AWD car but in most conditions you'll be just fine, especially because of the low center of gravity and 50/50 balance.
Just take a look at these two pictures: