All 3 are going to give you comparable power gains so that is a mute point, there are only so many ways you can bend a straight pipe to make it work.
The primary difference between these is going to be Sound. The ART Pipes will effect the tone of the sound, I don't believe the Berks are resonated? Or if they are then there won't really be a big difference between those or F.I.'s.
But it does kind of sound better when you're purchasing an F.I. CBE, to get the F.I. RTP with it at the same time...
