There's absolutely nothing wrong with a quaife or peloquin diff for road use or even moderate competition use (I have used one for the past several years in my ibiza and have won numerous events with it) - the preload only comes into play if you have one wheel in the air which is very hard to do with the amount of suspension droop on a leon. For anything other than a dedicated competition car, the atb diffs are fine and trnasform the car. The wavetrac actually remains to be fully tested having not been out that long.