My experience has been the same as Gasp, Steve & Mike's. I used box squats heavily this year, in fact almost exclusively and my quad strength went through the floor. I know Contreras has his quad activation study and he found more quad activation via Box Squats but I just can't see how that's true.
A proper deep, upright torso, knees extending forward, raw squat will nail the quads. (And before anyone say's it, if you do them correctly they will not hurt the knees.)