Skiing vs. Snowboarding: Which is More Difficult?

Question
Which do you think is harder and why?

Answer
Not an expert with snowboarding, but from experience and what I've heard, I think skiing is harder. Why?  Probably because your legs can easily go separate ways, and it's much harder to fall down while you're skiing.  It's easy to just sit down while snowboarding, despite the pain on the backside.  The hard part of snowboaring? Flat surfaces, avoid them at all costs.