I prefer using whatever is at my disposal to rest on or against to steady my shot. Either a rock, fallen tree, skidoo seat, my knees if need be, but pretty much anything to steady myself. I can hit vitals sized targets all day at 100 yards in the standing position at the range, but when I have a huge parka on, 18 pounds of snow boots, 4 layers of clothes, snotcicles hanging out my yingyang, and I am out of breath, its only fair and right for the animal I'm aiming at to do my best not to botch the shot. That means .........I use a rest. No matter what.
I just have never seemed to be able to duplicate shooting range conditions out in the field when I am hunting. Apples and oranges. I am ALWAYS out of breath when I come across game.