I think it?s impossible to compare CC and C2, CC uses Phyton and C2 uses HTML5, it?s a huge diference.
just for clarification, although you can script with python in cc, plugins are made in c++ and caps are compiled to cc's own exe format for events that run the plugins' c++ code, so it's much faster than pure python
but yeah, for now cc is much much faster, but html5 brings great possibilities. personally I'm working on a project that will combine the two. like a character editor online(c2) that can save characters you can load in your exe game(cc)