Here's my experience:
Grew up hiking with ex and current mil surplus all-cotton pants and button-up shirts: cold, wet, heavy, chafing. The boots were heavy, blister-forming, and like casts that induced tripping and sprained ankles.
UF-Pro: I have some of their pants; robust but probably too heavy for backcountry applications. I mainly just use them at the range/IPSC (internal kneepads are useful for stages that involve kneeling on gravel), and use Fjallraven Kebs for hiking.
Patagonia pants: Were a bit billowy on my and not a pocket layout I found useful. Also shiny and oddly silky ... felt like I was MC Hammer, and not in a good way.
Varusteleka have some interesting pieces - namely the Sarma wool pants and jacket, which
@Formidilosus has posted about. These are fairly heavy and likely for specialised uses. My experience in the snow all day is that I was toasty. They also have a synthetic puffy overpant which is fairly cheap compared with the hunting brands.
Lots of us here use Aclima Woolnet base layers (look for the dedicated fishnet base layers thread). I've heard that some militaries use them, but can't confirm. The Exo guys mentioned on a podcast that DFND also do a wool net, but I'm not sure anyone here has tested them yet.
Arc'teryx Leaf: I have one of their jackets (forget the model) that has mesh sides and an insulated front. I'm not sure it's the right compromise solution for everyone: I found under exertion, the insulated panels are too warm, but with wind, the mesh panels all for too much cold. My personal use case is now relegated to 3D field shoots in winter where we're not moving too quickly - and in that case, far simpler and cheaper items would probably do just as well.
Sitka Arrowhead line: A few of us have their jacket that has Polartec Alpha. I like it, but have found it to be affected by wind. Here's
@mtwarden's review:
https://www.rokslide.com/sitka-arrowhead-equipment-mdwi-hoody-review/ and Q&A:
https://rokslide.com/forums/threads...pment-mdwi-hoody-review-by-mike-moore.253383/
These last two are a good example of the .mil vs civilian question - I found an Outdoor Research mid-layer jacket that works better (for me) than the Arc'teryx or Sitka .. I think this issue overall is really piece-specific, and use-specific.