Waterproof knee pads are worth it if you frequently ski in wet or deep snow conditions. Spring skiing, heavy powder days, and wet coastal snow can soak through water-resistant pads over time, leaving you with cold, heavy padding against your skin. Waterproof pads use a full membrane or sealed shell that blocks moisture completely, keeping the padding dry and effective all day.
The trade-off is breathability. Waterproof materials trap more heat and sweat against your skin, which can make the pads feel warmer and less comfortable during high-output skiing. If you're charging hard in mild conditions, this can be noticeable.
Go with waterproof knee pads if you ski in the Pacific Northwest, ride deep powder regularly, or spend lots of time in spring slush. For typical cold, dry resort days, water-resistant pads offer a better balance of protection and comfort.