What you wear on your legs really makes a big difference to how you climb and how you feel while you’re climbing, by which I mean having a pair of strides that restrict and hinder full athletic movement are both a drag on your body and mind and potentially dangerous.
More than any other type of climbing, on a winter route you do not want to fall off, and the thing that has the biggest effect on this is being able to climb well and unhindered. High stepping, bridging and even the odd drop knee make climbing more fluid and effective. You can’t do any of these things in a pair of pants that feel as if they’ve been modelled on Paris Hilton or Ronnie Corbett.
I remember Dave MaCload complaining about how restrictive winter climbing felt when wearing a suit of Goretex armour. Sure it’s great when you’re stood on a belay in a hoolie, but once you start climbing it’s like opening a mars bar with your mitts on.
The upper body is important in this respect (having good arm lift etc), but it’s far more crucial when it comes to the legs. What’s needed is the same approach that you’d have if picking a pair of cragging pants, something that gives you 100% movement. Stevie Haston showed the way when he ditched his one-piece Patagonia shell and switched to just wearing power stretch, which although not appropriate on a day on Meggie, shows the approach one needs.
A well-cut, well-fitted pair of hardshell bottoms can do this BUT for most people it’s almost impossible to get those two things to match, meaning there is always some restriction.
Softshell is a better way to go, even if this means keeping a featherweight pair of hardshell pants in reserve. Basic Schoeller style pants worn over powerstretch bottoms will give you the movement and protection you need, while bottoms like the Paramo Aspira or Patagonia Speed Ascent bottoms give a similar degree of freedom but in a stand-alone package.
So when buying winter bottoms make sure you try out the ability to allow you to move, meaning doing the splits in the shop (well as far as you can), some high steps and drop knees. Also while you’re at it check how easy they are to have a dump in… not literally though, save that for the super scary routes!