I own a few pieces of Minus 33 clothing, in particular a long-sleeve undershirt that I love. They clearance a little bit of their stuff through their own website and I think on Amazon--if you're not too picky about color. It's good quality stuff. I'm not familiar with the other 2. I also have some light weight merino underlayers from Core4element, which are fine (especially for the price, as you can sometimes find them on pretty good sale). First Lite and Smartwool have good reputations, but I can't really comment, except on a pair of Smartwool socks I have.