There's lots of variables with strings--the material is just one. How it's made, the number of strands, how well it's made, nock fit, length of serving, etc. etc. etc. can affect performance.
You won't normally pick up a whole lot of performance with a FF type material vs. dacron, all else being equal. I like them for the increased durability and decreased stretch/creep.
Properly made, you will see little to no difference in performance between endless and flemish, as long as everything else is the same.
Chad