ORIGINAL: bigbulls
Personally I would rather have a chisel type of head to shatter bone some before the blades and the rest of the arrowgets there. Provides a more open path through a bone, like a shoulder blade, for the arrow to followthan a COC head will.
Having said that, if you are pulling low enough poundage then neither one will get far though a shoulder and the COC will give easier penetration through soft tissue between the rib cage.
I'm with BB on this. I've seen several COC tips get damaged which effects the rest of the arrow all the way through.
For a COC head, you can'g go wrong with Magnus heads, or Montecs for that matter.