I've had both. Unfortunatelly my CB died due to an ich outbreak in the tank. It was a great community fish and left all my coral alone.
I then got a flame. So far, it has also been a great community fish and has left all my coral alone.
IMO its just a matter of basically which color scheme you like. The CB will be cheaper, both have been super fish for me.
In either case, just make sure you have a bunch of lr and keep them well fed and they shouldn't bother your coral. Both definately liked to forrage (sp?) on lr constantly. I would also recommend supplementing with algae sheets. My flame likes red algae, my CB liked green. Good luck it is a tough decision to make. Let everyone know what you decide on. :happyfish