One difference that I just found out is that the Quaife maintains scoring of the inner bore of where the halfshaft seats in the differential. This is to keep it lubricated and in turn prevent seizure. My Wavetrac does not have that and the stock open diff does. Just one small attention to detail I suppose. Did you decide yet OP?
Refer to FBIS's review.
http://www.e90post.com/forums/showthread.php?t=365404