Vertical compression straps run from the top to the bottom of the pack, letting you cinch down the overall height of your backpack. This is especially handy when your pack isn't full — instead of having a half-empty bag flopping around on the slopes, you can compress it into a sleeker, more stable profile that won't throw off your balance.
The big advantage of vertical straps is how well they pair with diagonal ski carry. If you like carrying your skis diagonally across your back (a popular method for backcountry touring), vertical compression straps won't get in the way like side straps sometimes can. They work in harmony with that carry style, keeping your load tight and your skis secure.
Choose vertical compression if you're a backcountry skier who frequently adjusts your load throughout the day — shedding layers, eating food, or accessing gear. Just keep in mind that if you prefer A-frame or other ski carry methods, side or dual compression might be a better fit.