I voted for the Pro Circuit T4 and not just cause I have it. I have had two other pipes before this one (a cobra and a FMF) and I honestly think this one is the best from my experiance so far with its tuneable end cap system, awesome over all power delivery, and very strong build quality tops them all.
I would say yoshi, also not because I have it, but simply because it runs awesome at constant midrange and top end riding just as long as a headpipe is put on with it. Just the slipon used to give me a super powered midrange and a little bit of lows.