Low breathability isn't necessarily bad—it actually has a real sweet spot. If you're skiing in bitterly cold conditions, pads with minimal ventilation help trap warmth against your body, which can be more comfortable than having cold air constantly reaching your skin. Think deep winter resort days or night skiing when temperatures really drop.
The tradeoff is moisture management. Low-breathability pads trap heat, but they also trap sweat. Once you stop moving and cool down, that dampness can make you feel chilly and uncomfortable. This is especially noticeable if you're wearing the pads under your ski pants, where there's less airflow to begin with.
Low breathability works best for short sessions or very cold days when staying warm outweighs ventilation. For all-day skiing or any time you're working up a serious sweat—like hiking to backcountry lines or spring skiing—you'll likely be happier with medium or high breathability instead.