Both will work as I have used both in matches. If I had to pick one I would pick the 2C as it give your wind hold marks in the lower quadrants for hold over corrections or wind holds and the open center is small enough it doesn't effect accuracy like some open center reticles can. Actually it helps when shooting very small targets. Those are the main two differences between the 1C and 2C. The rest of the main reticle is the exact same.
The open center is great, especially for precise shots on small targets as Rob mentioned. The lower "Christmas tree" gives you more capability in different scenarios where you may be prohibited from dialing turrets. Just another tool in the toolbox when you need it.