I would have thought that at the exact moment of the split the value would half but then lets say for example everyone sold their BCC and bought BTC, bitcoin would then jump back up to it's former price (or close to) and BCC would crash to zero. Now obviously that won't happen it will be somewhere in the middle.
My advice is read about them both and go with the tech you believe in. If you don't know or understand find a few well known people you trust and see what they say.
Personally I'll be selling my BCC.