from what i know mike they are basically the same. the main difference is the curved plates that allow for the traction when a wheel is lifted. pricewise almost identical although shipping from the uk might be costly and doubt it will get here any sooner than the wavetrac!
the quaife has a great reputation on the m/b forums with e55 cars pushing well in excess of 550 ft/lbs torque without any failures. theres a few write-ups on the install also

initially autotech was the distributor of the quaife until they went full time wavetrac production