xdmkiiAdvantage of vertical baffles: one is able to shift the down up and down the channels to where you need extra warmth. Also the down is unable to fall to the sides as is possible with horizontal. Advantage of horizontal baffles would be the ability to shift all the down from underneath you (where you're compressing it) to the sides/top.
CardamomteaYes, all of what Cardamomtea said, but the biggest difference between vertical and typical horizontal baffles is how the bag will drape against you. To some degree as a side sleeper but especially if you are a back sleeper, the vertical baffles will conform to your body much better and become a more efficient insulator, both by reducing air space to heat and by greatly reducing or eliminating cold spots from compression/tension on the baffles. The latter can be reduced in horizontal baffles by good design, material choices, and amount of fill. If you want to maximize the benefit of what vertical baffles can give, then you combine those with really ultralight fabrics and good down, and then you can use a little less down to achieve the same-ish warmth...but we're talking an ounce-ish in a bag give or take...important to some. Zpacks' design is a good one, most people say the temp ratings are a little on the cool side.
dday1937Yes. You have to take people's claims with a grain of salt sometimes, especially as quilts have become the new norm and everyone starts buying them. Many people expect them to be like a bag and don't realize that they are warmth-rated a bit differently, plus everyone's personal thermostat isn't the same. There seems to be consistent feedback that Zpacks' and Enlightened Equipment's are not quite as warm as the temp ratings given to them. Hear less of that from companies like Hammock Gear, UGQ, Nunatak, Katabatic, etc. That is mostly owing to each of them using more down per similar temp rating.