Single-lens goggles are best avoided for skiing and snowboarding. Without dual-pane construction, there's no thermal barrier between the cold outside air and the warm, moist air near your face. This means they fog up almost instantly on the slopes—and once fogged, your visibility is gone, which is a genuine safety risk when you're moving downhill.
You'll typically only find single-lens goggles in the cheapest budget models or rental packages. They might get you through a single dry, cold afternoon, but in any humidity, precipitation, or during exertion like hiking to a line, they'll fog relentlessly. They also provide poor insulation against wind and cold.
If you're on a tight budget, look for goggles with at least dual-lens construction and a standard anti-fog coating. They're still very affordable and perform dramatically better. The small price difference is absolutely worth it for clear vision and a safe, comfortable day on snow.