Polyester shell snow pants are a solid choice if you're a casual or occasional rider on a budget. They're lightweight and comfortable, and they'll keep you dry and warm for a typical day on the slopes. The main trade-off is durability—polyester isn't as abrasion-resistant as nylon, so it's more likely to show wear if you're regularly sliding on snow, brushing against branches, or taking spills in the park.
If you only get out a few times a season or mostly stick to groomed runs, polyester pants will likely serve you just fine. They're also a great option for kids who outgrow gear quickly. However, if you ride frequently, venture into backcountry terrain, or want pants that last multiple seasons, investing in nylon or Gore-Tex will pay off in the long run.
Think of polyester as the "get the job done" option—perfect for light use, but not built to take a beating year after year.