Either can build into good wheels, or bad ones depending on all the other factors, so it shouldn't be a material question, but a quality one.

However, one important consideration is the braking surface. If using only for racing where braking is more about speed management vs. hard stopping, carbon wheels are OK. But carbon rims don't handle the wear and tear of braking in the real works well. This is most important in urban or hilly areas where brakes get lots of hard use.