I have used the UA base 3 for a couple years now and am well pleased. Have not used the smartwool which probably is a great product. I like to dress in layers starting with the UA , wool or chamois cloth shirt, NF jacket for stopping wind and a fleece or wool outer jacket for quiet and warmth.For extreme cold, below zero, I use Arctic Shield as a final layer. Use the same gear top to bottom. I like insulated, gore tex boots and gloves, a wool outback hat (mine has ear tabs). I own and use some gore tex outer wear at times but find it to be a bit more noisy than fleece.