Winter pants with vents?

RAB Bergen pants.

My usual winter pants are softshell pants. They breathe great and wick well, not to mention shed snow and light rain nicely. I use the REI ACME Pants, but there are tons of options from Marmot, Patagonia, Arc'teryx, and the like.

I feel like waterproof/breathable pants are more necessary in shoulder seasons but less so in the winter, especially when I dig out my tall gaiters.

If you're really dead set on WP/BR, try the REI Kimtah pants, which are made of eVent and a bit lighter than the Taku. The pockets are mesh-lined, so they vent, and eVent material is significantly more breathable than Gore-Tex and REI Elements.

I also use the REI Acme pants (16.9 oz) on the coldest trips and the REI Mistral pants (13.3) if a little warmer. They are size 30" X 32" and are made of Shoeller material.

The rest of the year I usually wear shorts or Eco-mesh pants.

For snow or rain? Bushwacking in mind? I've seen snowboarding and ski pants with thigh vents, but nothing you would want to hike or snowshoe in. Outdoor Research Igneo pants have inner thigh vents with a published weight of 22.5oz. The review I read said that you will get cold air where it might not be wanted. That should keep your pace up :)

For cold/dry/snow conditions, +1 on the softshell that suits your weight and budget needs. I like lighter softshells that can be supplemented with long johns. If you are camping, you would want the long johns for sleep anyway. Tall gaiters and soft shell pants make a good mix in snow, keeping the snow out of your boots and adding the extra waterproof layer up to your knees and the top can breathe.

For cold/wet rain, I like polyester long johns with a breathable rain shell. My Marmot Precip pants have full length zippers and can be left open at top or bottom– there are snaps or Velcro tabs to keep the ends together. Vary the weight of the long johns to suit.