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 335i E92, 6MT, Le Mans blue - Quaife LSD, JRZ RS Pro, JRZ camber plates, Eibach ERS, full M3 susp, custom toe arms, Powergrid end-links, SS brake lines, brake ducting, Michelin PSS, UUC SSK, ETS FMIC, ER CP, Perf. Exhaust, VAC RSIK, Sparcos; work by VAC Motorsports in Philadelphia