You probably won't loose a lot of performance. The main advantages to using a FF type material, in my opinion, is the increased durability, lack of stretch and creep, and reduced hand shock. In the long run, I believe it's actually cheaper to use a good FF type material, because the string will last longer, and you can use fewer strands so you get more strings per spool of material.
With proper tuning and the right strand count, a FF type string can be made just as quiet or quieter than dacron. The only "down" side to FF type materials is some bows aren't made for them, and the added up-front cost.
Chad