In reply to multisport:
I disagree with just about everything you've said!
I have a Gamma SV, which I've worn for the last 3 seasons ice climbing and skiing. I wear a long-sleeved thermal top underneath, and if it's very cold, a Marmot Dri-Clime. It is almost totally waterproof (the fabric itself is waterproof but the seams aren't taped). In Rjukan a couple of years ago I had water running down the arms of the jacket yet I stayed dry.
The advantages over a traditional shell are not just that it's tighter and more flexible but that it's warmer, vents better and suitable for a far wider range of conditions.
The MX is rated for "Moderate" conditions (whatever the hell those are, and the SV for "Severe" hence the difference in our experiences, no doubt.