>>1912296Haversack is for foraging or trapping. Its easy access, and a haversack filled to the brim with mushrooms, plants, smal game stays relatively light.
If you're going to be covering ground with gear, obviously backpack. Anything heavier than 5kgs/10lbs on the side of you gravity center instead of in the middle of your back is enough to unbalance you, which means potential injury on rocks/heights
