Actually, in that picture, Preloader looks lower than either Iraqivet or JusticePete.
I will rephrase my answer to the original question: installed in a manner following instructions, neither should lower a car more than the other. I make that statement due to many "allegations" but to my knowledge no proof that the BC BR is a Chinese clone of the Pedders Xa. Enough allegations to indicate to me the very real possibility of truth.
One would expect if there were significant differences, other than quality of construction methods, those differences would have come to light by now. To my knowledge, none have.
All three are so low, and in his commentary JusticePete says he could go lower but at the sacrifice of rideability, that it seems the only way to get a definitive answer would be to line the three up, side to side, and then measure.
Laborsmith