Price is comparable so in theory the hybrid offers the better performance? Ferrari used the hybrid extensively in the F40, why is it that supercar builders these days use pure carbon, even when the panel is to be painted?

Because cf is so strong, light and rigid, it's great for cars, planes and rifle stocks (what I use it for). Materials like Kevlar and fiberglass require far more layers to become rigid so parts end up heavier and heavier parts make baby Jesus cry... Because they aren't rigid, fiberglass and Kevlar will bend more before they break so, they are useful where those properties are desirable.