Not sure what testing you're really looking for but both the Perrin and PW will hold up to about any boost you can throw at it. The process west has more surface area, the perrin is overall larger based on cubic inches.
I'd say the one with the most surface area is going to cool better, and I would have bought the process west but it came out about a month after I got my Perrin. Also, from all reports I've heard you can run STi layout turbos, so any turbo without the new 08+/lgt flange on it. That is a nice bonus if you ever plan on upgrading the turbo, it opens up a lot more options.