The stock ones tear pretty easily. If you're going to swap turbos a few times more you'll tear another stocker, and it's worth going aftermarket for durability. I just ordered a Perrin for this very reason... mine is torn and I expect to test more turbos. Stay away from junk like GMS, FMS etc. as compsurge mentions.
Don't type things you wouldn't dare say to someone's face.
Obligatory 'build thread