I have a Quaife and here's what I like about it:
-Proven technology. Been around for decades
-Quiet. No difference vs. stock in this regard
Can't comment on the Wavetrac. But the Quaife - the dependability of these things is worth a lot.
2011 BMW E92 335i, 6MT, M Sport, Le Mans blue - Michelin PSS, Quaife LSD, JRZ RS Pro, JRZ camber plates, Eibach ERS, full M3 susp, custom toe arms, Powergrid end-links, brake ducting, SS brake lines, UUC SSK, ETS FMIC, ER CP, Perf. Exhaust, work by VAC Motorsports and Bavarian Specialties