Front squats are king for quads. Back squats suck when compared. It's very easy to keep your back straight. If you don't, the bar will crush your delts.
But they still hurt my left side so seldom do them. And going ATG just occurs normally for some reason when doing them.
Gonna give them a try again next monday but not on the smith machine. Tried it before, did not find the movement to be natural feeling at all. But works for some.
Nothing like front squatting some other dude's max back squat, lol...