The Patagonia simple guide pants are polyester, and I don't think they'd stand up to very much glissading. I think something with nylon would be more durable, but would repel less water and dry slower.
I just got a pair of Marmot Scree pants which are nylon (polyester inner). I've worn them on one dayhike in the mid-50's with a good wind, and they were very warm at that temp and fit great.
A soft shell isn't really a rain shell replacement. It works great as a shell in dry cold conditions (less than 15-20F) when snow can be brushed off rather than melting in. They do block some wind and dry faster, but they're still wet clothing in wet-cold conditions with precipitation or snow contact.