My brother got into cross country skiing this year and i've tried it a few times myself. I've only been to a couple of skiing trails, but they were both seemed fairly well groomed. I've also done quite a bit of riding on various types of snow this year, and would consider the groomed cross country trails to be "top notch" for snow biking. (I don't ride on them because I don't want to ruin them for the skiiers)
When I was watching bits of the olympics, I wondered if a pro cyclist would beat the skiiers if he was riding with them on the same trail. So I'm wondering if on a groomed traill (i'm thinking skate ski trail), is skiing faster than biking?
I've also never ridden a "real" snowbike (like a pugsley), so I wonder if you could challenge a classic skiier through deepers now on a proper bike.