Which E6700? The 2.66 GHz Conroe or the 3.2 GHz Wolfdale?
"C2D" in this context is talking about the Conroe, but there is so much confusion that you are better off talking about specific chip models.
If you are comparing the 3.0 GHz E5700 to the Conroe, I would say the E5700 has a slight edge. The greater chip speed should balance the Conroe's larger cache. And the E5700 will overclock better. And it is less expensive.