A couple of things. Both are cut 'athletic', Kuiu a bit more so. I'm 5 ft 8 about 155-160, 41" chest, 33" waist. Both Large jackets fit, the Kuiu is a bit snug in the arms with a light puffy under, the Sitka fits well with a Kelvin Lite hoody underneath. Pants seem to be right on with Kuiu maybe being a bit more generous than Sitka. I have a size 32 Mountain pant, size 33 Timberline. I wear one with base layer, one without, fit is perfect.
I would call both companies, discuss your size and they'll guide you. Black Ovis is also really good to deal with. I would order a set from both companies, try them, don't wear them outside. Keep the one you like, send the other back. Or send both back if you don't like them. For your measurements, I'd throw First Lite in the mix. They are cut way more generously than Kuiu or Sitka and make as good as quality. In FL, I wear medium in their jackets and have room for puffy under. I have a couple pieces of their gear, notably the woodbury jacket. Its my whitetail stand jacket.
Yes what I would do. Kuiu sleeves suck azz, and that is putting it lightly.Both in length and in width. specially in the forearms.
