i like to box squat as i feel its the best functional exercise there is, but i will still full squat to prevent any block in my squatting, alot of people only go paralell, but the prob is, if they drop in to deep they'll end up stuck at the bottom if they cant full squat, i tend to rep out on full squats and hit low reps on box squats, just my preference, full squats for me have led to some issues with pains in my tibalis..

but as they say " you aint squat till you squat " < very true