a few questions about layering systems

i've been rock climbing for years and have dabbled a little bit into mountaineering but this spring i accompanied a friend on a proper alpine climb and I. AM. HOOKED. i'm looking to buy a few things during the down season so i have them ready to go for next winter. i've got plenty of upper body layers and i'm not worried about them. my primary questions have been about pants

i've always just worn a hard shell pant with large, open zip-vents for skiing, touring, and the little mountaineering that i've done. i've seen a lot of people touting the benefits of softshell pants, especially for mountaineering, ice climbing, and alpine touring. why are softshells so much better? people reccomend hard shell for the NE because of the moisture but for climbing here in CO people reccomend softshells. why? is there anything specific about winter softshell pants that seperate them from regular hiking/backpacking softshells? what should i look for in a winter specific alpine climbing pant?

my next question: i've seen some people reccomend an insulated puffy jacket and pants and a small, light sleeping bag in leiu of a heavier sleeping bag for bivvying. I've heard great things about the mountain hardware compressor pant but can't find them anywhere online. can anyone reccomend an equivilent item from a different brand?

Places like CO and UT are so dry in the winter (low humidity, dry snow) that soft shells can work. Places like the NE are so wet (high humidity, lots of thaws) that hard-shells are most popular.

Soft shells breathe better, keeping you more comfortable (ie. less drenched from sweat) than hard shells.

In addition to what has been said by others, soft shells can be tighter fitting, while allowing a greater range of motion, and offer more friction on rock and ice. However, unless you actually have a "problem" with your hard shell (I.e. too much sweat retention), I wouldn't feel compelled to buy a soft shell.

For features, I recommend researching the "gamma" series of soft shell pants from Arcteryx. The various models have pretty much all the bases covered (side pockets, low bulk belt, lace hooks, reinforced high wear areas, etc.). I have the gamma LT pants, and I use them for EVERYTHING (summer alpine, winter alpine, ice, rock, hiking, trail running, yoga). My hard shells haven't seen the light of day since I bought them.

Puffy pants are definitely a worthwhile investment. I know that Montbell and arcteryx make suitable puffy pants. The key feature is full side zips, so you can throw them on, while wearing crampons and a harness. I also like having a fly that allows my belay loop to stick out, while keeping my hips insulated.

Outdoor research mithrill