I think it all depends on how good a skier you are... haha. Jk! I think the early Zeiss M rangefinders had problems keeping rangefinder alignment, with many off right out of the box. This was fixed later and I think most problems of this sort went away with the later bodies. But any rangefinder is susceptible to vibrations and shock skewing the alignment, its just a matter of how hard the shocks are and how long they last, but I have heard of tales where people have taken rangefinders on long motorcycle trips strapped to the back or to the tank, and the cameras worked fine. id bring both, the xa for the skiing and the zeiss of the other moments. I wouldnt want to worry about whats in my pocket the whole day and miss out on enjoying the snow.