I love merino wool, and when the thickness is right for the boots, it is also my choice. But, I've got bad feet(flat arches, hammertoes, weakened tendons, that all will require surgury some year soon....when I can't stand walking on them any longer!) I have a devil of a time finding boots that fit BOTH of my feet comfortably. For me, sock VOLUME is the key to getting through a long day in the high country. Some boots require a thick wool sock, sometimes a poly liner or thin wool inside another wool sock. I have a lot of wool sox in various thicknesses and use different insoles and othotics to make my feet feel right in the boots that I have.
All mountain game spend their days walking around on vertical slopes. You will too, and with lots of sidehills. You may think your boots fit great and are broken in well. But if your feet can move around inside them too much, you could be miserable and almost hobbled by the third day. I want my feet to fit snugly inside the correct boot, and -for me-a major factor is adjusting sock volume to the boot. Note: I also use several pairs of boots on most hunts and switch them every day or so.....so, more sock changes to adjust.(I know, if you're horse- or back-packing, one pair of boots is the rule....then, you just have to live with whatever you've got.)
Good luck and good hunting.