I can only speak for the injen...It rocks. Definite power difference. It can be had for ~215 shipped, I believe. Spool's kit is 175$ (on sale now for less) but it doesn't replace the goofy ass plastic s-bends after the MAF to the turbo. For this reason alone I would go with the INJEN. Don't forget...ION is coming out with theirs too, but there are duties etc. since they're in CAN, I believe.
The INJEN will provide a cool, Kenworth Truck-like turbo spooling noise, and amplify the BPV (now a pissed off turkey noise..sounds like fftttrrrr on release). It's all up to you, though...