pipercross - hands down.
Of course, I am a bit biased being that I own one, but the reasons I based my opinion on are:
You have the option of pulling air from right up behind the lower grill and also have the option of disconnecting the hose if weather turns to total crap and you are concerned about sucking up water.
Foam is going to flow much better than paper.
K&N tubes are metal and retain heat more than the ducting hose for the piperX
Used in WRC cars...that's gotta say something.