I have 4 different brands of merino base layers (two of which you mention) and SmartWool is my favorite. I have hunted in below 0 temps and in heavy snow hunting elk in CO and deer in SD. I have only tried a heavier weight than the medium weight 190's once and I did not care for it. Just my opinion, but the 190's and lighter weight base layers, breathe better and work to wick away sweat quicker than the heavier weights. I use my second layer and or outer layer for warmth, not my base layers.