I suggest neither, you need different tires for the winter- trust me, snow chains are ok but I have seen them brake and you do not want to hurt your baby, because I've seen it happen - they can snap back and whip around the side of the body, don't even take your Z in the mountains, you absolutely cannot drive a Z car in the snow - TRUST ME - I LIVE IN WISCONSIN = SNOW. There is too much torque and the car is too light that you will just end up at the bottom of the mountain, going down the side not on the road. The other thing is that car is so low that it banks the snow and can throw off your steering. DON'T TAKE IT IN THE MOUNTAINS! I have a Z4 and I tried to drive it in the snow last winter, (with a lite covering over the road - you even lose control).