I own both. And several others.
Kuiu is cheaper than Sitka.
Kuiu is also typically lighter weight than Sitka.
I like the Sitka knee pad systems better than the KUIU knee pads.
I like the Kuiu leg length better than the Sitka length.
I like the Sitka tack strip in the waist band. Keeps my pants from pulling down under the movement of my pack.
I LOVE the belt that comes on some Sitka pants (Mountain pant and equinox.)
Sitka often uses a better reinforcement around the inside ankle.
Sitka is way easier to get your hands on.
I don't think one is better than the other. One is cheaper than the other. Some articles have options that I want in Sitka, some in Kuiu.
thats why I own both.
For a warm weather pant, I cant say enough good about the Kuiu tiburon pant. That is one sweet hot weather pant.
For high altitude backpacking, I love the sitka ascent pant and the montane super terra pants.
For sheep and goat excursions I use the Sitka mountain pant. I shredded a pair of Kuiu attacks doing this stuff. Mountain pant is much better for this.
Kuiu guide pants are great for cooler weather.
You get the point, we don't need to get into down jackets, shirts, and rain wear.
Each offering from each company has a use.
The question is, what fits your uses best?
Who cares what the internet fan boys say?
Shop the products, based on your needs. Get what fits your uses and budget the best.
Sitka gear is highly desired by many. Its price is high. Can you afford to buy it? Can you afford to replace it if it gets hammered?
Kuiu gear is great. Its hard to get on demand. It has a high price as well. Not as high as Sitka, but still expensive. Can you afford to buy it? Can you afford to replace it? Does it meet your needs and wants?
First lite gear is also spendy, its less desired when compared to the other two.
I am not one to wear camouflage when not hunting. I do all my scouting and preparations in non camo clothes.
I would buy a pair of Montane super terra pants before buying either the Kuiu or Sitka offerings.