I opted for the FRN. I own plenty of things made of CF...in my mind the material is all about function. I have never seen any knife that benefits functionally from CF greater than it could with G10 or FRN. Aesthetics are a whole different story.
CF costs a LOT compared to G10 (and FRN, but it is hard to directly compare raw material costs). FRN is very economical from a manufacturing stand point, and while some do not like the looks, it performs VERY well. CF by contrast is expensive to buy in sheets, expensive to cut and sculpt (it is hard on blades). CF simply costs more to mass produce knife handles with. Many people feel that the aesthetics warrant this cost (I personally do not).
These are just my opinions (and a couple are probably facts). I think if you compare the Stretch II to most other knives made with identical (or even similar) materials, you will find that it is a good value!